The Wikipedia community has an informal hierarchy of core principles — the first being to strive for NPOV. The second simply demands reasonable degree of civility towards others. Even if "civility" is just an informal rule, it’s the only term that can apply, and it’s the only reasonable way to delimit acceptable conduct from the unacceptable. We can’t ask people to love, honor, obey, or even respect another, but we have every right to demand civility.
One essential definition of civility is to treat others as you like would have them treat you. However, in reality, it is not always enough just to treat people in the same way that you would have them treat you, because people may have different preferences for how they like to be treated. For this reason being civil relies on the use of empathy to realize that others may have different preferences of treatment than you do, and that a form of behavior that you might not personally find unpleasant could be experienced as unpleasant by others. Importantly empathy, includes the ability to realize that others may also have difficulties being sufficiently empathic, and that perceived lack of civility in others does not necessarily stem from bad faith, but could come from users having different norms of behavior or personality.
Incivility is a vicious cycle because people who experience uncivil behavior from others will usually retaliate, escalating and polarizing conflicts and threatening or impeding collaboration.
The problem 
Wikipedia as a whole is not especially respectful of other contributors. This directly affects the quality of the community experience at Wikipedia. By hurting the community, the quality of articles is affected as well. This creates a cycle of incivility that reinforces itself, and in some cases conflicts between contributors over one article can expand to involve additional people and additional articles.
Petty examples that contribute to an uncivil environment
- use of rudeness or profanity
- racial, ethnic, and religious slurs
- judgmental tone in edit comments ("fixed sloppy spelling", "snipped rambling crap")
- belittling contributors because of their language skills or word choice
- ill-considered accusations of impropriety of one kind or another
More serious examples include
- personal attacks
- defacing user pages
- calling for bans and blocks
Incivility happens for example when you are quietly creating a new page, and another user tells you, "If you’re going to write a pointless page, could you spell-check it?" Escalation occurs when you reply, "Mind your own business."
This style of interaction between Wikipedians drives away contributors, distracts others from more important matters, and weakens the entire community.
When and why does it happen? 
- During an edit war, when people have different opinions, or when there is a conflict over sharing power
- When the community grows larger; each editor does not know all the others and may not perceive the importance of each individual to the project—so they don’t worry about maintaining relationships that don’t exist. Reputation does not count as much as in a smaller community.
- Sometimes, a particularly impolite user joins the project.
Most of the time, insults are used in the heat of the moment during a longer conflict. They are essentially a way to end the discussion. Often the person who made the insult regrets having used such words afterwards. This in itself is a good reason to remove (or refactor) the offending words.
In other cases, the offender is doing it on purpose: either to distract the "opponent(s)" from the issue, or simply to drive them away from working on the article or even from the project, or to push them to commit an even greater breach in civility, which might result in ostracism or banning. In those cases, it is far less likely that the offender will have any regrets and apologize.
It should be noted that some editors deliberately push others to the point of breaching civility, without committing such a breach themselves.
Why is it bad? 
- Because it makes people unhappy, resulting in discouragement and departure
- Because it makes people angry, resulting in non-constructive or even uncivil behavior themselves, further escalating the level of incivility
- Because people lose good faith, resulting in even less ability to resolve the current conflict—or the next one
General suggestions 
Preventing incivility within Wikipedia 
- Prevent edit wars and conflict between individuals (constraints on editing are set by the project—essentially a community answer)
- Restrict access to Wikipedia for some class of people more likely to be offensive (reducing openness)
- Force delays between answers to give time to editors to calm down and recover and to avoid further escalation of a conflict (protecting pages, or temporary blocks of editors in case of conflict)
- Use positive feedback (praising those who do not respond to incivility with incivility)
- Use negative feedback (suggesting that an editor involved in conflict should leave Wikipedia or simply allowing the editor to leave—whether or not that person was the offender or the one guilty of the offenses—in order to reduce the level of conflict)
- Apply peer pressure (voicing displeasure each time rudeness or incivility happens)
- Solve the root of the conflict between the offender and the other editor(s) or the community—or find a compromise.
- Block certain users from editing specific pages that often trigger incivility
- Create and enforce a new rule—based on use of certain words—that will allow temporary blocking or banning an editor using them more than a certain number of times
- Request the use of real names to force editors to take responsibility of their behavior (although this is generally considered not desirable on Wikipedia)
- Filter emails by the offender, or filter mail based on certain keywords and reject emails to the Wikipedia mailing list with those words
- Decide that incivility and rudeness can’t be avoided in such a project, and accept their existence.
Reducing the impact 
- Balance each uncivil comment by providing a soothing or constructive comment
- Do not answer offensive comments. Forget about them. Forgive the editor. Do not escalate the conflict. (an individual approach)
- Ignore incivility. Operate as if the offender does not exist. Set up a "wall" between the offender and the community.
- Revert edits with a veil of invisibility (&bot=1) to reduce the impact of the offensive words used in edit summaries (the comment box)
- Decide that incivility and rudeness can’t be avoided in such a project, and accept their existence.
Removing uncivil comments 
- Strike offensive words or replace them with milder ones on talk pages (this is often seen as controversial, as is refactoring other people’s words)
- Remove offensive comments on talk pages (since they remain in the page history, anyone can find them again or refer to them later on)
- Revert an edit with &bot=1, so that the edit made by the offender appears invisible in Recent Changes (do-able on IP contributions, requires technical help for logged-in user)
- Delete (entirely and permanently) an edit made by the offender (requires technical help)
- Permanently delete an offensive comment made on the mailing lists (requires technical help)
- Replace a comment made in an edit summary by another less offensive comment (requires technical help)
Management of incivility during the mediation process 
Parties sometimes attempt to negotiate an agreement while one party is not ready to negotiate. For example, if the source of the conflict is a specific point in an article, dispute resolution may be impaired if discussion is still clouded by an uncivil exchange between both parties. It is best to clear up that issue as soon as possible, so disputants can regain their balance and clarity when editing.
Explain incivility 
Some editors are badly shaken by uncivil words directed towards them, and can’t focus on the source of the conflict itself. It may help to point out to them why unpleasant words were used, and acknowledge that while incivility is wrong, the ideas behind the comment may be valid.
The offended person may realize that the words were not always meant literally, and could decide to forgive and forget them.
It can be helpful to point out at breaches of civility even when done on purpose to hurt, as it might help the disputant to refocus on the issue (controversial).
Rephrasing disputants’ comments 
During the mediation process, a third neutral party is in contact with both disputants, ensuring communication between them.
The role of the mediator is to promote reasonable discussion between the two disputants. Therefore it is helpful to remove incivility voiced by User A, in rephrasing comments to User B.
- For example, if User A and User B are flaming each other by e-mail through a mediator, it might be best if the intermediary turns "I refuse to allow Neo-Nazi apologetics to infest the Wikipedia" to "User A is concerned that you may be giving too much prominence to a certain view."
Rephrasing flames publicly exchanged before or during the mediation process 
At the end of the mediation process, the mediator may suggest that the disputants agree to remove uncivil comments that have remained on user and article talk pages. The editors might agree to delete a page created specifically to abuse or flame the one another, and|or to remove all flaming content not relevant to the article discussion, and|or to refactor a discussion. This may allow disputants to forgive and forget offenses more quickly.
Similarly, the disputants might agree to apologize to each other.
Suggest apologizing 
Mediation regularly involves disputes in which one party feels injured by the other. The apology is an act that is neither about problem-solving and negotiation, nor is it about arbitration. Rather, it is a form of ritual exchange between both parties, where words are said that allow reconciliation. In transformative mediation, the apology represents an opportunity for acknowledgement that may transform relations.
For some people, it may be crucial to receive an apology from those who have offended them. For this reason, a sincere apology is often the key to the resolution of a conflict: an apology is a symbol of forgiveness. An apology is very much recommended when one person’s perceived incivility has offended another.
If all else fails... 
If an editor feels the need to be uncivil, he/she should do that elsewhere, not on Wikimedia projects.