My original suggestion was: Change the minimum character limit for comments to an “Are you sure” instead of a requirement - similar to the minimum for question titles.
I think that Sid Meier had a good idea: "new users can't post short comments, intermediate users can post short comments but are asked if they're sure, and advanced users can post short comments without any prompts"
I think that we should make sure we tell the new users why they can't post short comments (so they learn) and also tell them that higher reputation will remove the restrictions.
Also please do not make any more comments on this question that just prove the system can be tricked.
Edit: Looks like we better make sure we don't let the high rep users forget the reason that they were blocked from short comments to begin with
Edit: Oh Well It looks like this idea is not going very good. Perhaps you should still upvote my question if you want the limit changed... and this question: Can we get rid of the threshold of 15 chars for comments?