The tag is ubiquitous. The tag is useless. The tag is ugly. The tag is, quite simply, bad.
eyebrows_visible_through_hair is a tag that has no feasible use whatsoever. It describes a tiny inconsequential detail that exists on 95% of posts with visible eyebrows and bangs, born either through an artist's laziness or their desire for a character to be more expressive. Nobody is searching for the former, and there are much more specific eyebrow tags at one's disposal to search for the latter (v-shaped_eyebrows, raised_eyebrows etc.).
An argument against this tag's destruction in the past has been that we can exclude it to search for (or that we should be tagging the rarer inverse case of) eyebrows_behind_hair, which is now a moot point due to such a tag already having been created. Even if a group of eyebrow enthusiasts were to wriggle out of the wormwood to protest because "it would help to tag old posts with eyebrows_behind_hair", the fact remains that EVTH likely applies to millions of posts on the site, yet is present on less than 900k of them (of which a tiny fraction are the over 2 million posts from before 2016). The false positives more than drown out any actual results, and as such this tag is not remotely useful even for this niche purpose.
To get this tag to a state where it provides any benefit at all would require a herculean effort from a great number of builders sifting through millions of posts, all for the result of a tag that is barely valuable at all. Not to mention that the effort would need to be ongoing - there is a reason this tag is already missing from such a vast number of eligible posts. evazion put it best in topic #15668 when this was proposed over three and a half years ago:
The fact is that eyebrows visible through hair is practically nonexistent on posts before 2016. It's on 15k posts out of 2.2 million. I'd wager it should be on at least a million. Nuking the tag makes no difference when it may as well not exist on anything more than two years old anyway.
The reason it's not tagged on older posts is because nobody actually cares. I find it difficult to believe that anyone geniunely has a use for this tag when nobody seems to have even noticed that it's almost completely absent on everything more than a couple years old.
If you think these tags are worth having, then show it by populating them. Otherwise it's meaningless to talk about how these tags should exist unless you intend to populate them, and frankly, and I don't believe anyone seriously does. If you actually do try to populate either of these tags, I think you'll quickly see what an enormous waste of time they really are.
There is no part of this statement I do not agree with. EVTH is now present on about 30k posts from before 2016. In over three and a half years, that number has only increased by 15k even with likely a million untagged posts. If this doesn't prove how little we actually care for this tag, then I don't know what will.