Thread:Help talk:Adding tooltips/Inline tooltips are sad

I don't think that adding a whole parser function that can only draw an icon and add  attribute is worth it.

At least you could use jQuery tipsy plugin, that is bundled with MediaWiki and allows block HTML tags in the tips, as well as nested tips.

There is no need to define a parser function: a template and several lines of JavaScript code in MediaWiki:Common.js or a gadget will do the job.