This thread is unhealthy and needs to be locked.

I don't know where I read that, but it makes sense that "the accused" must have a platform (the thread) to respond to the accusation made against them. Surely it follows an unlocked thread that is referenced in the Flag is that platform?

Flag not supported at this point given:

The terms of creating Flags is quite clear in that the thread cannot be a self moderated one (this thread is self moderated) and the thread cannot be locked.   You did not create the thread, therefore, you cannot guarantee that the thread won't ever be locked.