I kinda like it, but it should be operable for the mods (so it flags it for them to check, or whatever automod eventually shows up can hide the post until it's cleared)...
I like the ability to edit, but agree that some kind of limitations should be on it. Requiring mod review of a URL change would, at least, put one level of check into the system. The other option would be to simply allow only mods to change the URL. That doesn't prevent a bad actor who is a mod, but that seems less likely than a standard user.