Don’t you find it annoying when someone comments with just a smiley? Or a “thanks”? On quite a few forums you have to leave a comment with a minimum of 15 characters to be able to comment, but WordPress doesn’t allow you to set such a threshold. The minimum comment length plugins does exactly that.
If you install this plugin, you’ll get a new option page with 2 input fields, in the first of which you can set the amount of characters people should use at minimum for their comment to be accepted. It defaults to 15, which is a pretty nice number.
If people then leave a comment of less than 15 characters, WordPress dies on them with the message “Error: Your comment is too short. Please try to say something useful.”, or whatever other message you decided to give to them, as this is the second option you can specify in the backend: