The touhou characters Chen and Rin are notable nekomatas.
Should their cat form be tagged as nekomata as well as their human form or should it all be left alone?

I don't really see much point of tagging all their picture with that(even in their cat form) as I thought that tag would already be applied with them or something. It would be the same having them tagged as youkai. Or tagging all post that include Remilia_scarlet and Flandre_scarlet with vampire.

We already know what they are(or at least most of us) so it won't make too much of a difference.

But if it helps with simplier and/or better searching I'm not going to object.

Practically speaking it seems you could search cat_ears multiple_tails and get the equivalent (along with all the other nekomata-like cat girls).

If you want nekomata, at least search cat_TAIL multiple_tails and cat multiple_tails. nekomata would tell you that the multiple_tails tag belongs to a cat(girl), not a kyuubi that happens to be in the same picture. With that, Chen and Rin would only count as nekomata if both tails are visible (and I'm sure many wouldn't be happy with that).

I believe we've made it clear enough why Remilia/Flandre don't get the vampire tag.

Rin is actually a Kasha, and not a Nekomata, but that's beside the point. For things like vampires, where the character generally has wings and fangs(2 things that many non-vampiric characters also have) labeling them wouldn't exactly be a good idea. But for things like nekomatas(catgirls with 2 tails) and kashas(catgirls with 2 tails and human ears as well), distinction could be a good idea.

But, we don't exactly know if a character is one of those things if the series' wiki, or the artist(in the case of original characters) doesn't provide info for, or otherwise. So i'm against it.

Kasha is not distinguished from nekomata because they have human ears. They are different because the concept of "nekomata" refers to long-lived cat that have their tail splited, while "kasha" is a youkai that steals corpses of people who were evil when alive. The general thinking - but no hard belief - is that kasha is a type of nekomata. Thus basing on ZUN's illustrations to tag these two are wrong.

If you see anything look like the picture I linked, or if the artist say they are drawing the personification of kasha, tag it so. Otherwise leave it out. A drawing of cat or monster cat (not catgirl) with multiple tails can be tagged nekomata.

S1eth said:
I believe we've made it clear enough why Remilia/Flandre don't get the vampire tag.

Unless they're visibly doing something undeniably vampire-ish, such as drinking blood.