Template talk:Head
It looks like this does not work properly at the first call on a page, unless the parameter is 1. See also Template talk:Head/broken.
{{head|1|abc}} gives: =abc=, or in a new paragraph:
abc
{{head|2|abc}} gives: ==abc==, or in a new paragraph:
abc
{{head|3|abc}} gives: ===abc===, or in a new paragraph:
abc
{{head|4|abc}} gives: ====abc====, or in a new paragraph: