Careful, now...
There are good reasons for not be able to edit, after posting. Some folks would play games, and go back to change their wordings, delete a statement or two, just because they are competitive in their fierce argumentativeness.
It can be bad enough as it is, with some folks twisting words around, and inventing/claiming things others supposedly, but did not say.
An edit button with a link to revisions maybe? Sounds clunky...so maybe that's too much?
Regardless, whatever changes you make --- you can change back, or change again, if you don't fully like the results.
Missing a few typos is nothing compared to changing entire posts. Eventually, nothing could make sense if enough is "edited."