This can't be correct, since the system can't detect when comments break the guidelines. It's either based on flags or downvotes, or perhaps just total number of comments. It's definitely not based on karma, since I'm rate-limited.
Another possibility is that it triggers when a moderator gets pissed at a single one of your comments.
The rate-limiter is applied manually when we notice that an account is posting a high volume of guidelines-breaking comments. The way we notice is by reading the threads, which we spend much of each day doing, or when we're alerted to guidelines-breaking comments by flags or by community members emailing us.
Another possibility is that it triggers when a moderator gets pissed at a single one of your comments.