Yes. And our rules allow you to force even background color on the viewer. Which they can then try to override with CSS or other client-side stuff.
All that fancy markup is probably useful only
- on homenodes,
- in old posts from before spoiler tags that used background color and font color to hide spoilers,
- and in a few posts of eyepopslikeamosquito (but don't even think of copying him).
We want to keep supporting some of those uses unless it causes too much problems. If someone wants to make their posts unreadable, there'll always be ways for that, and I don't think there's much point trying to fix that by banning particular attributes unless a particular sort of abuse gets too common.