So no_bra is aliased to invalid_tag, but its wiki page says "see braless" which is a tag with quite a few posts.
I personally feel like this is a reasonable tag and one that people might want to search for. There are cases where you can see a character doesn't have a bra under their shirt, like:
post #4340777
Should no_bra be revalidated and braless aliased to it, matching no_underwear, or should braless be invalidated too?