My apologies; I didn't mean to insult you! And you're right; writing a bad review isn't a callout.
I've thought about doing this, but to your other point, if they're comfortable ignoring my messages I feel like they may just ignore the threat of a beware.
Additionally, one of these artists is someone who's had multiple bewares written about them (I unfortunately learned about this after commissioning them), so I feel like they really wouldn't care if I did write a beware.
I hadn't thought of that! I'll try that; thank you.