If the editing could be limited to a maximum of 6 characters, that would cover most incidences of clumsy typing and still stop misuse by those who write abuse and then wipe it after they're sure the intended target has seen it.
Most forums reserve editing for the moderators, these days, it seems.
An alternative would be a 'preview' page, with a second button to press to submit the post (wiki-like system). This would be great as typing some characters leads to unrecoverable loss of a lot of typing downstream of the characters you had no way of knowing that the edit box would reject.
Another alternative would be a 30-60 second window for the poster to spot the error and hit the edit button. Abusive posts could get through but might not last long enough to be seen.