it would cause rows...because people would be able to say something then deny it or change it etc and make others responses look wrong
heres a novel idea ... check the post before pressing submit ... if you have time to check it afterwards and go back and edit , you have time to read through it before pressing send...
We can sorta get round the whole "but you can change a nasty post later on to cover your back" argument...kinda, if it automatically put a "Edited at...then a time" on the end.
Just make any changes by the OP 'soft edits' - where the original is preserved and can be seen by the Ed and the mods - that's the way it works on most sites.