In Austio's response to this question, it needs a single character edit which is critical to the response (@user should be @users). However, due to the edit length restriction, I could not make the edit. By looking around in meta, I sensed that the edit length restriction is primarily to discourage bots that do minor edits to get the rep bonus.
If this reasoning is true, my suggestion is to enable arbitrary edits, but then restrict rep bonuses to edits beyond a specified length. That way, those sincere about adding value even with a couple of characters will do it, and bots craving for rep will be discouraged from short edits.