shimamura_youmu

I personally deem this tag (shimamura_youmu) useless as it equals the konpaku_youmu beanie query (or more precise: konpaku_youmu beanie scarf), given that beanie is seldom used for any characters Youmu interacts with in images.
Now I don't just delete tags I don't like (especially when someone bothered enough to write a wiki for it).
Is there any use for this tag?

Also, I noticed 3 character tags for Wriggle in different clothes.
wriggle_nightbug -> princess_wriggle -> dark_princess_(princess_wriggle)
= 3 character tags if the only character in the image is dark_princess_(princess_wriggle)
I've changed the latter two to general tags as they're just alternate versions (clothes) of wriggle_nightbug and will always be used together with the wriggle_nightbug character tag, but I'm still not happy with the choice of names for the tags.
The name makes you think that dark_princess_(princess_wriggle) is an alternate version of princess_wriggle who is an alternate version of wriggle_nightbug. Why would dark_princess need princess wriggle in brackets and not the original wriggle, why not just call her dark_princess_wriggle?

princess_wriggle is a kind of meme that spawned from some doujin before influencing other artists, notably resulting in the creation of the character dark_princess (actually 黒姫 - see my comment on post #650740).
Since it became some sort of sub-universe I thought the (princess_wriggle) qualifier was appropriate (especially if there are other characters to expect, which I'm unaware of at this point).
I don't mind either way anyway.

> shimamura_youmu looks valid to me. Should be treated the same way than okamisty, so I guess the tag is fine.

So (princess_wriggle) doesn't refer to the character, but to a doujinshi with the same name?

Yes. Possibly not the actual title (though I have very little doubt about that), but the main idea around the story.

Princess_wriggle is exactly the same as okamisty in how they came about, the latter is only more popular on Danbooru. However I'd suggest delete the dark_princess_(princess_wriggle) tag, which is completely redundant. princess_wriggle dark_persona is enough.

*look around*
I changed gothtia into general tag too. Like the case with shimamura_youmu, this is nothing mystia_lorelei gothic_lolita can't cover.

Unpopular miscellaneous memes should be eliminated until they are solid enough to merit a tag.

Agreeing with rantuyetmai here, I think. Character variant tags are used somewhat sparingly (awakened_miki, miku_append) so we want to find solutions using existing tags where possible.