In reply to KTS915.

Third, the notion that this involves “rewriting” a plugin is ridiculous. Would you say that about adding custom CSS that overwrites what is included in a plugin? Of course not.

I assume you are referring to what I said, this obviously depends on a plugin, and if you can run it in a "no css" mode then I will assume that almost no harm may happen, but plugins which rely on say a P element having a 20px top margin might break if you remove that style rule or change it. The problem most likely will not be apparent when you make the change, but when you upgrade the plugin. JS is obviously even worse in this regard.

So yes, if you change styling you will need to test every plugin upgrade to still work well with your changes as there is no way a plugin author can test all the possible modifications people might make to the plugin's CSS.