Thank you very much for your speed!
But for a better understanding would it not be better to re-add the "locked" button next to the move button?
You should be able to provide a reason for editing. This reason should then have it's own markup to make sure people see the post has been edited and it's reason.
One addition to post editing would be to put a time limit to it, say, 5 to 10 minutes. After that, a post cannot be edited.
@planner Great idea! I fully support that!