TheatreFan4 said: "John Adams said: "Dynamic IP addresses are more common than static, so restricting by IP address wouldn't be effective."
I mean, I've been on plenty of forums before where it's been effective. It's not 100% and there are ways around it but it's more work in the way of the person making the attempt."
Yes, there are ways around it, and for every (1) successful account deletion, the troll just simply replaces it, so (IMO) it becomes a game of whack-a-mole.
As I've written before, I believe the best offense is ignorance (as kdogg also writes). I also try to make a conscious effort not to preach or scold in threads where I see other posters feeding the troll. Less is more.
But... your situation is different. The troll is sending you PMs, which definitely is a situation that should not (and likely cannot) be ignored. I solved it for myself by electing not to accept ANY PMs from anyone. I know that's not a solution that works for everybody.
I wonder if there is a way to preempt delivery of PMs until the receiver grants approval. For example, before the PM reaches an Inbox, there might be a preemptive message saying, "[UserX] wants to send you a private message. Do you want to accept?", followed by an option to select "Yes" or "No" (maybe "Always" or "Never"?).
Again, this is my own, curmudgeonly choice, but I just find it easier to set that option "Allow Private Messages" to "No" in Account >> Settings.