Justin Rhymes
 

I have looked for hours and am having no luck, but I'm positive Justin Rhymes should be on bard faction, not merchants of highpass faction. After killing guards in highkeep and eventually becoming kos, these two(Justin and Tarn) were the only merchants I could sell to.

As I say I've looked as much as I can, and unfortunately I can't find any proof. I found no mention of him becoming kos, though. I have found many instances of people calling him a bard, which makes sense since he's selling bard songs.

Is anyone else able to back me up on this?

Yes, he should be on League of Antonican Bards.

Fixed, pending update.