It seems a lot of over-posting comes from the famous "karma: 1, created: 30 seconds ago" accounts, so it may make sense to impose limits based on time as a user

It seems a lot of over-posting comes from the famous "karma: 1, created: 30 seconds ago" accounts, so it may make sense to impose limits based on time as a user. (Karma may not work as well, as I could imagine a spammer creating 100 accounts and using them all to upvote one another's submissions.)