This suggestion is coming up with increasing frequency in various forms; one of my colleagues expressed amazement this morning that we don't already do this - he'd spent the morning cleaning up after an abusive comment-author, only to find this person had kept right on leaving abusive comments the whole while.
Journeyman and Catija have suggested a couple of ways in which this might be problematic, but in truth we need not speculate: such an automatic-ban system already exists in Chat!
...this system is not exactly well-loved. While I don't think it's as bad as folks make it out to be, it's hard to ignore the fact that it often has the opposite effect from what is desired: abuse-banned folks often come back angrier and more abusive than when they left.
Of course, comments aren't supposed to be chat. But that raises an important question...
Why aren't we rate-limiting comments based on how they're used?
If the intent of comments isn't to chat up other users all day long, then why does the system allow them to be used this way?
- Some users are in the habit of leaving dozens, even hundreds of comments on dozens or even hundreds of posts... Every day.
- Some users are in the habit of conducting long, detailed back and forth conversations in comments under their posts.
- Some users regularly leave multiple comments back-to-back under the same post.
- Some users do all of the above even when 50-75% or more of their comments are deleted on a regular basis.
...and the system does very little to discourage any of this. There's a tiny bit of rate-limiting in terms of how fast you can post comments, but nothing stopping you from posting just a bit slower than that all day long, every day, on as many posts as you wish to.
For a moderator, the only options for handling persistent comment abuse are:
- Suspend the user from the site
- Do nothing.
- Laugh madly while the world burns (functionally equivalent to #2)
So from a user's perspective, they get absolutely no pushback at all until suddenly all of their privileges are gone... And on larger sites where comments can readily go unnoticed, this may take months or even years.
In essence, the system and UI facilitate - even encourage - abuse, even while flaggers and moderators are expected to stop it.
Instead of automatic bans, I'd suggest something like this:
Limit everyone to some number of comments per day and some smaller number of posts on which they can leave comments. Let's say... 100 comments / day and 50 commented posts / day by default.
Reduce both of these limits severely if the % of deleted comments for a given user exceeds some nominal threshold over the past week. For the sake of discussion, let's say anything over 20% gets you knocked back to 20/10, and anything over 50% puts you at 2/1. Yeah. If more'n half of your comments get deleted, you only get to post two comments on at most one post per day.
For the purpose of these tests, ignore auto-generated comments (duplicates, canned off-topic reasons, review deletion comments) - those are supposed to be deleted in many cases.
Show the number of remaining comments below the comment form whenever a user starts to compose a comment.
My prediction is that this system would dramatically reduce the number of noisy, snarky, rude comments even for people who never hit the limit, simply by making it obvious that they're using up a limited resource.
But for those determined to push forward, it would add real teeth to flaggers' and moderators' cleanup efforts by drastically reducing authors' ability to generate huge numbers of worthless comments.