Can you add a notation that shows when a member edits their posts?

It is very frustrating when you reply to a post and then the OP can still edit their original post with impunity. We all say stupid stuff, but we shouldn't be able to make it go away without at least acknowledging we've edited/removed our original remarks

That happens after a certain amount of time passes. Have you thought about using the "Quote" button to capture what somebody says before they have a chance to remove it? Their original un-edited post will appear in your post and they won't be able to touch it.