There should be a minimum limit on the post length.  Say 80 characters.
Anything less than that should be deleted.  If someone posts repeated "reserved" words, jail him for a year at his current membership level.

Another option is to remove the membership and activity levels all together.  They are pointless.  Most people know who the "Hero Members" are.
Limit number of posts per day to say 5 for all users is another thing that can be used to limit pointless posts.