I've seen “tag spring cleaning” meta threads on many sites, where people are invited to raise problematic tags, one tag per answer. They usually end up in a mess: after the first few, nobody pays attention to anymore, and being able to discuss things only in comments is stifling (is this tag really problematic? should it be disambiguated? should the meaning be clarified? …).
Such threads are pretty common on private betas, too, owing to a superficial reading of the blog post that's linked on private beta meta¹. Those threads usually end up in a mess too, for exactly the same reason as the spring cleaning ones.
Is there ever a case where a general tag discussion thread is useful², or should tag discussion threads always focus on a specific tag or a specific family of thematically related tags³?
¹ Which should be this clearer and more up-to-date post instead, but that's another matter.
² I confess to doing it myself once, when I had less experience of private betas, and it didn't end up in a mess — because it didn't end up with one tag per answer. But that was rather unusual.
³ e.g. “should we have tags for individual countries/authors/species/…”