Here's the thing, this thread wasn't started out of the goodness of the OP's heart in trying to help people. I don't know the back story, but it sounds like she thought she got blocked, she got ticked off, started this thread figuring people would agree with her (because everyone is going to agree it's cowardly to send something nasty to someone but then not be willing to receive it back) and she probably figured the person who sent the PM would see it and see that everyone thinks he/she was wrong.
So, even though I'm sure the OP will deny it, this thread was started to call someone out on something and make them feel bad. But it was done in a very passive agressive manner. Which, it's a public message board, so everyone has the right to do it. But if you are going to dish it, you better be prepared to take it. This thread wasn't started with nice intentions and the OP shouldn't be surprised when some posters decide not to play nice on the thread. If this were a thread where someone was just being nice, maybe thanking their DIS friends for helping them through a tough time, and had a lot of spelling or grammar mistakes, I doubt people would call the poster out on them. Because when someone is being truly nice, most people reply with kindness.
But if you are going to start a thread with mean intentions, don't expect the people on the thread to play nice.