The categories plugin should get a proper markup to display nested categories, i.e. nested unordered lists. This saves additional classes or inline styles for indenting nested classes because nested ul and li elements can be addressed via the CSS cascade.
Would be awesome for threaded comments, too! :)
See, I'm not so sure about that. The categories list could be considered a navigation list (but not a nav element), but the comments most definitely are not a navigation element. Is a ul (or even ol) really the proper HTML element for comments?
I think of a list of comments. Semantically, nesting lists for threading makes perfect sense to me. It also opens up new possibilities for styling nested comments. See these examples:
I have given this some thought over the past couple of days. I guess my main concern remains: Is a list with just one item (which will happen in nested uls for threaded comments) still properly marked up as a list or is this using HTML as presentational markup?
Update: Garvin basically ruled out comment nesting since it's really expensive performance-wise. I'm actually quite okay with the current comment nesting, but I'd still like to have it for categories, which apparently is possible.