As of forum #229899: Same artist. Their studio is called Aeru Studio. I didn't add the studio socials because Fuumeh also works there and they might hire new artists in the future, which could create problems for tagging them in the future.
As of forum #229899: Hirota-kei/Beaskie's Twitter account was a third-party. I removed the Twitter links, corrected the posts and added other links I found. In other words, Hirota Kei has nothing to do with Andy, so I'm renaming the tag.
EDIT: Beaskie is a different artist btw. Beaskie is the Artstation username and Beask is their name.
mandi0pan seems to be cecii's current handle, but someone should look into it further (and see if a new tag is in order, as the pixiv in the former indicates the artist has changed their name).
kasuteru and pokepen also have the same Twitter link, but all other URLs listed are different as well; has anyone confirmed whether mk kiu and hoshikuzu stella are not the same, because I remember how the latter's entry was beyond fucked a while ago; and are murderhouse and wakaho riku the same, or is this a Nanakamado Anno/Merryweather situation?
Idk about Mandi0pan/Cecii, it'd be better to try contacting the artist.
kasuteru source:https://twitter had two posts, which I changed to Pokepen. Still, I'm not sure, they're either two different artists that happened to use the same name and got mixed (Kasuteru AKA CASTELL had a FC2Blog named pokepen, I can't say anything about the Yfrog/Twitpic accounts) or the artist avoids relating the "possible" NSFW with the SFW/personal account (They're inactive on Pixiv and Tumblr but still relactively active on Twitter).
Same artist? Under artist #159245 links, there are users with the names bewbchan and furrchan. There are no links connecting them from what I can tell, but I saw https://twitter.com/furrchanart already added before.