Just like "Member", "Privileged", etc, a merely cosmetic tier for users with verified artist tag, since that badge only shows on posts, but doesn't on user profiles or comments, latter of which has the existing tier titles and having an "Artist" title can add the tiny bit of context for any discussion, no need to introduce yourself as the artist anymore!

Since you say "no need to introduce yourself as the artist anymore!" I assume you're suggesting it should only appear on posts by that artist (and otherwise treat them as a regular user on any other post)? If it was a tier like member/priv/admin it would show everywhere so that would get a little misleading.

I do quite like this idea. I've seen quite a few websites that highlight the original poster in the comments, which isn't quite relevant to us because 90% of posters aren't the original artist, but in the case of verified artists? I think it would be great.

An "artist" account rank would inherently be less accessible than other forms of verification (janitors can verify you, but they can't change your account rank), it would exclude janitors/moderators/admins who are also artists, and if you're an artist commenting on somebody else's post that's not particularly relevant.

Showing checkmarks in the comment listing would be more appropriate.