S1eth, I'll concede on post #1395908 since the ribbon doesn't match, as minor as that may be, but c'mon. An uncommon costume from the game it originates in should be reason enough to tag it, lest it become lost in the shuffle for anyone looking for her in that costume.
We have however used curiosities_of_lotus_asia to tag those particular costumes. While not a game, it is a copyright tag. However those costumes are extremely unique and distinct so I think the exception is warranted. In contrast, the official game costumes don't vary that much.
Yeah we typically do it for printworks, like WAHH + Mamizou.
Just because we haven't before doesn't mean we can't now. All along we probably should've been tagging UFO Marisa, for example. PCB designs, I have no problem tagging, although it might be difficult to determine what's just a character in a scarf. It's also easy enough to pick through character + scarf for anyone who wants to find them. Then some like Reimu don't change much at all.
That's not the case with HM Marisa, though. Or UFO Marisa, as I said, both having no way to be found otherwise. Which is why I say it's more than fine to tag exceptions like them. HM Ichirin I'm on the fence about, but she has kesa, at least, and can be found with Ichirin + kesa. But tags can be missed, of course.
Alternatively, Pixiv employs Hopeless_Masquerade_Ichirin or something similar. In our case, kumoi_ichirin_(hopeless_masquerade) or kirisame_marisa_(undefined_fantastic_object), kirisame_marisa_(ufo) or something, which would be no more worse than futatsuiwa_mamizou_(human) or any other character with a qualifier for alternate designs or forms.
