I know sometimes mods lock threads at their own discression, especially at boards where they are a local moderator. At least when s thread gets moved there's some forum notice being posted. But for locking a topic there's nothing to signify it was a moderator action.
I just think it would be a nice courtesy if mods would just add a post before locking a topic to justify why they felt it should be locked. It's good to put this info on the record for future reference. And also from what I understand, since the OP can unlock a topic locked by a mod, a post by the staff member that took the action would prevent misunderstandings.
- If a mod locks a topic and the OP is not comfortable with it, it is the duty of the Op to create another post asking why their post was locked.
- Moderator writing the last post before locking a thread is a nice suggestion. But moderation is best when you don't know who moderated you. A moderator making such a post before locking will expose him to everyone that he's the who locked the thread.
- Since you corrected yourself, a user cannot unlock a post locked by a mod.