I'm not calling him out or anything, but S1eth and I have some pretty different ideas as to what deserves the hopeless_masquerade tag. Some game tagging he and I agree on, like post #1415340 which isn't all too indicative of double_dealing_character, where you wouldn't know it was about DDC without following the artist, but there are others.
I know how to tag Touhou titles has come up sometimes and that any three people probably have no consistent idea how to tag game titles between them all, but with some conflict here and there once again, I felt it might be time to revisit it in one thread.
I think most of us have already agreed upon rules, like cast pics. Yes, they deserve the tag. But then, how much of the cast need to be present? Do the playable characters need to be there? Is just the main antagonist group without the one or two minor, plot irrelevant bosses enough? Anyway, with the playables, include everyone. If it's just the main antagonist group, then include the game tag, without everyone.
Then there are some images tagged ten_desires with just toyosatomimi_no_miko, mononobe_no_futo, and soga_no_tojiko. It might just be mistaken tagging that was never rectified, but the game does revolve around them, while as I see it, perfect cherry blossom doesn't really revolve around yakumo_yukari , yakumo_ran and chen. Though it's moot. With so many pics of just the three out there and not wanting to bog down the tag, along with the longstanding unofficial Touhou policy of not creating or using new tags / pools just to group a household or gathering of related characters, and not wanting to drown the tag, I'd say kaku_seiga and miyako_yoshika or konpaku_youmu and saigyouji_yuyuko would need to be included before including a game tag.
In other words, once again, a full, main antagonist group, at least. Although this is one I know people would definitely disagree on.
But the main thing that caused me to speak out is... costumes, alternate outfits, and colors... along with references, parody, and such.
When it comes to Touhou's printworks like curiosities_of_lotus_asia or wild_and_horned_hermit I and some others tend to use copyright tags for costumes exclusive to that series, that wouldn't be found otherwise when just searching a character tag. These costumes simply tend to be uncommon and near impossible to find without the corresponding copyright tag, but it hasn't exactly crossed over to game titles.
As to how that applies to hopeless_masquerade for a few examples of which I feel are deserving, see post #1393202 and post #1415194 (Marisa in her HM costume, which is again extremely hard to find without said tag). post #1418327 (Marisa in an embellished version of her costume). post #1431868 (Ichirin in her HM palettes). post #1395908 is interesting, since it includes just one mistake in her hair ribbon design, but everything else matches HM, including a reference to the focus on her legs in the game, but is one I let go
References to HM I tagged recently include post #1428930 (Kokoro scenario reference), post #1430345 (Mamizou's spellcard), post #1431159 and post #1432654 (Futo's entrance and Kokoro's victory pose), among other edits.
As for other games when this could be used, there's Marisa's blue costume in SA that could be tagged with subterranean_animism, and Marisa in her undefined fantastic object costume, which are both distinct enough to identify, but hard to search for. In the case of UFO Marisa kirisame_marisa apron just gives you, well, Marisa in any old costume of hers w/ apron instead of her UFO costume. S1eth brought up everyone's scarfed costume in PCB, too, which could be tagged with some discretion. Reimu or Sanae are remarkably more difficult since they change so little, but if there's significant reason to, they should get the same treatment.
Frankly, short of kumoi_ichirin_(hopeless_masquerade), kirisame_marisa_(curiosities_of_lotus_asia),kirisame_marisa_(undefined_fantastic_object), kirisame_marisa_(hopeless_masquerade) like Pixiv sometiems uses, or similar, I think we could stand to tag any irregular, uncommon costume with the tag of the work it appears in, even when there are other factors with which to identify them. I'm sort of on the fence with Ichirin since it has just about become her regular costume and has the potential to bog the tag down, and can be searched for with kesa kumoi_ichirin, but hijiri_byakuren with her prayer beads and ajirogasa or Mamizou's leaf hat? Totally absolutely.
Bottom line, cast image, reference, parody, costumes... short of finding another, better way to properly categorize and separate official alternate costumes so that they're easier to find, should all be fair game for Touhou game titles.