To figure out artist names yourself, looks like you'll want to read howto:pixiv's "Artist Naming" section, and howto:artist. Of course, knowing how to read and look up Japanese will make things easier, but you might be able to get by with howto:artist's tips for simple cases.
Zansnae793 said:
http://www.pixiv.net/member_illust.php?id=3704024
and
http://www.pixiv.net/member_illust.php?id=5810557
and
http://www.pixiv.net/member_illust.php?id=809198
and
http://www.pixiv.net/member_illust.php?id=8988534
3704024:
Pixiv display name = 茶交 = chamaji (kanji reading is given by the artist here. ヂ becomes ji according to howto:romanize)
Twitter display name = 茶交
Name given on personal website = 茶交
Seems clear to me, chamaji.
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5810557:
Pixiv display name = 吉田。 = "yoshida." (reading is from their website URL's "yosidaya" and the fact that this is a common Japanese name).
Twitter display name = 吉田。
Name given on personal website = 吉田。
Circle name = 吉田屋。 = "yoshidaya."
Pixiv username = kbkbhihi
Twitter username = kbkbhihi
"yoshida" is too common of a name, so it needs a qualifier. But I don't think the circle name of "yoshidaya" would help much as a qualifier; "ya" roughly means "room" here, and it's a common suffix for circles. So I guess the next best qualifier is their username, kbkbhihi.
Also, the artist seems rather intent on using a dot at the end of their name. Seems there's a few other artist tags that respect the end dot too, such as yellowpaint. and kamaseinu. So assuming that is what we generally do, I'd go with yoshida._(kbkbhihi).
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809198:
Pixiv display name: 栗月 = kuritsuki (reading is from their Twitter username, and the fact that these are common readings for these kanji)
Twitter display name: 栗月ロリ (just has "loli" at the end)
Seems fine to use kuritsuki.
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8988534:
Pixiv display name: 川´_ゝ`) (no way this is getting in the tag)
Twitter display name: うー☆みん (ignoring the star, this seems to be "woomin" going by the username)
Pixiv username: woominwoomin5
Twitter username: woominwoomin5
woomin doesn't conflict with any tag. I imagine it'd have some conflict potential among Korean names, but those aren't so common around here. So that seems fine to use IMO. If there's any doubt then woominwoomin5 is another option.