@Pollux I understand the ethical question behind why and in principle I agree. But there are exceptions to the rule.
Example. Some threads aren't designed for conversation, such as job listings or classifieds. In these cases this really isn't a concern.
Secondarily, it seems to me that the admins of the forums should be the ones deciding what the rules are on how content is deleted, and how much power to give their users.
Ideally, a plugin would allow you to set rules, based on the category of the thread. But that's just my two cents.
If nobody has a solution to this, then I'll build the plugin in the next few weeks.
Thanks for having this dialog with me and explaining the ethics of the design.