I feel like there's no polite way to recommend blacklisting a specific artist. I would personally suggest just having a line in there about how artists can also be blacklisted but not listing any specifically.

After all, consider this: unlike other tags, where the type of content is clear from the name of the tag (you know what you're blacklisting if you put male/female on your blacklist, for instance), with an artist tag you have to look at their art to make a decision about whether or not it's something you want actually to blacklist... So having it as a suggestion doesn't actually save anyone from seeing the content in the first place. In other words, unlike the rest of the suggestions on the list, the main advantage of including a tag on the blacklist suggestion list does not apply for artists to begin with.

So yeah. I think it's fine to just mention that it's a possibility without mentioning any names specifically. There is no lost utility there.