You post, I start to reply, you change, I post, you clarify. The ability to edit a post is a good thing because often after sending one can think of a better way to phrase something, want to edit it, or want to add something.
I dont see the problem. If someone feels they wanted to reply to an original version of a post then auto-quote it and be done with it. If there is a problem with the original then UT can look at it.
Question - why do you think email systems and most other on-line forums don't allow this ?