Almost as if there's a group of accounts that have to be babysat due to their unwillingness to be sheep, and by rate limiting them, it lessens the amount of effort required to monitor them.
Outright banning the accounts would look bad, and cause the accounts to start over in a way that would be difficult to catch at first.
Edit: I did find out a way around the rate limiting, in a fashion. Through editing.
Mine is too, but just to about 5 comments an hour.