This is how I understand it.
Once they've been convicted, I don't think they have any expectation to anonymity at all.
Before conviction, a place like MS has no way to investigate claims. Therefore there is nothing to stop people from accusing anyone of anything. Which in the short run could do some good, but in the long run would turn this place into a magnet for the scum of the earth to come and seek revenge on anyone who had wronged them by falsely accusing them of being an abuser.
Allowing unproven accusations here would also allow people to come on here and claim that victims were not victims but fellow abusers, just to mess with them. Most people wouldn't have the gall to do that, but some would. Once you open the door to accusations, a lot of innocent people can get hurt and this place very quickly becomes unsafe for vulnerable victims.
I think if an individual wants to write an autobiography and is willing to take the heat, more power to them. But a message-board can become a tool of the wicked very quickly if just lets accusations run rampant.