Hence the reason people should not PM others and say, "Don't even think about replying to XYZ post in the ABC forum." It is inappropriate and against community guidelines to send a PM like that (because it is unsupportive).

If you don't want Member ABC to reply to a post, you can't stop them because we don't have such a mechanism here (and it would be a silly mechanism to begin with). You can, however, ignore members you don't want to read. That's the way to accomplish the same thing with little of the hurt feelings the other way causes.

DocJohn