Merimask Goes On And On

Explain to them. I run a site for teenage writers, and they're quite capable of understanding copyright laws. We come down on them HARD if they break that, whether they break it in writing, art, or anything else. Most of them take it fine and say 'oh ok, I'm sorry, I didn't know', and I point them in the direction of some info on copyright law, and ask them how they'd feel if someone stole their work. Sometimes they go nuts. The worst I've had was some kid who thought it was hilarious, and after I banned him, he posted my novel on another site with just the name of the main character changed. After that I tracked him down on every writing site he was a member of and warned the admins. Unfortunately most didn't care (he's now a moderator at one of the sites!). So, that's my long-winded way of saying you should try to prevent it before it happens. Personally I'd go the way of putting some standard spiel in the description of each deviation that effectively says 'thanks for admiring, but no, you can't make one'.

As for being old and answering lots of comments, I don't have those problems, so I have no advice.