Disclaimer: I know that this has been brought up before. But it is my single biggest gripe with the tags on this site, and I think it deserves another discussion. I'll try to explain why.
As it stands, there is currently no way to search for (human/anthro)_on_feral such that you can specify the sex of the feral compared to the sex of the human or anthro. This is, to my mind, a major problem.
Most people who I've talked to about this have strong preferences one way or another. Someone who's looking for female human/anthro and male animal, for instance, is not the same sort of person who'd like female animal and male human/anthro.
Now, I know not everyone who has an interest in feral art is necessarily a zoophile. But, it's worth addressing from that angle, because it raises a rather strong point. The research I've seen seems to indicate that zoophilia is most similar to a sexual orientation. Which means I can draw you an analogy for why this tag distinction is important. Imagine, for a moment, that we didn't have male/male or female/female tags. Instead, we had the "homosexuality" tag, which encompassed them both, and furthermore, there was no way to distinguish between the two while searching or blacklisting. That would clearly be a problem with tags. I posit that it is just as big of a problem to not have gender-distinguishing tags for the (human/anthro)_on_feral tags (at least, for the people whose interests that is relevant to).
So, though it has been proposed before, I propose once more, three tags, which would, I think, mostly solve the issue:
male_on_feral (implies male, bestiality)
female_on_feral (implies female, bestiality)
intersex_on_feral (implies intersex, bestiality)
I think, combined with the existing orientation tags, this would work in most cases.
Two anticipated objections:
"We try to avoid gender-specific tags"
Yes, but that's why I drew the orientation analogy. I think this is a special case, in the same way as female/female, intersex/male, etc., are still valid tags.
"This would be a lot of work"
Yes it will. So I offer the only thing I can: If you want, I'll take up this project myself. I think I can get the entire bestiality tag converted eventually. Fairly quickly, relatively speaking, if anyone else decided to help, but that would, as I just said, not be necessary.
So there you go. My objections, arguments, and offer. Like I said, I know it's been discussed before, but to my mind, we haven't actually resolved it, so I think it should be discussed again.
Updated