You're doing it wrong. Make the tag "knucklecurve" and add the pixiv id to the artist entry.

I'm also reachable through PM. I don't see how else to add the ID, though... Care to enlighten me?

With a comment, more people are informed that pixiv ids don't go in the artist tag. There will be a pixiv id field in the next version of danbooru, but it's not deployed yet; for now, you can put the id in the notes, or stick the artist's pixiv page in one of the url fields.

That'll be good if the name is not fairly common. What if you encounter artists that have names like watanabe or takahashi only and they don't have a home page?

Then you go curl up in a corner and wait for death.

Haha.

Anyway, what's important is a unique identifier. Knucklecurve really is not a very common name so it's better for it to not have a pixiv id attached to it; it's easier to type too.