If you give me a list of tags, and where you think they should be allowed, I'll look at them. Can't promise more, I'm rather busy at present.

Please don't feel like there's any urgency here. I didn't mean to be complaining. These are actually quite small annoyances. Still there are some entities that I do occasionally miss being able to use...

• abbr and/or <acronym title="FOO">Foreign Optometrists' Organization</acronym>
• <cite>Citation</cite>
• <q>Short Quotation</q>. Maybe I'm being silly with this one, since we can still use traditional "quote marks".
• deleted text. This is semantically pretty much the same as <strike>strikethrough</strike>, except that <strike> is deprecated and <del> isn't. Again, maybe I'm being silly with this one. (Sometimes it's hard for me to tell when I'm being silly or not about things like this.) If <del> were supported, it would make sense to also support inserted text, as they seem to go together.
• It's tempting in some ways to add <style> to the list, but I can think of N ways in which it could be abused, so it's probably best left out.

<cite> happens to be the one I've used most often, forgetting that it wasn't permitted, though <abbr> when I do miss it is somewhat more bothersome.

As far as where they should be allowed, I'm not sure I understand the inner workings of the site well enough to say, other than that it's usually in an ordinary node body (such as either a root node or reply in SOPW, obfuscation, Meditations, ... you know, a regular node). I don't recall ever missing the ability to use any of these tags in a node title. Hmmm... in the chatterbox maybe though.