The how-to tag has no tag wiki but 37 questions covering widely different topics. I'd be inclined to associate 'how to' questions with support ("How do I use Stack Exchange feature X") but users have managed to tag discussions, feature-requests and even bugs with them.
I think how-to is a meta tag, not unlike the [best-practices] tag mentioned there and should be burninated/synonymized/merged. Thoughts?
Since I originally posted this, the tag has been removed from a few questions and as far as I can see it's safe to apply support to the remaining ones, as @PolyGeo suggested in the answer. That was previously impossible for me because "synonyms to required or moderator only tags can only be created by moderators", but @Sonic reminded me that circumstances have changed and I can no longer reproduce that error message, so they're merged now.