I'm not opposed to having the system automatically revoke comment privileges once a certain flag threshold has been reached, but that always got tricky in implementation when you consider the possibility of users ganging up on someone (perhaps coordinated through chat). When it comes to taking away privileges, I like being able to say "the system did it, you brought that on yourself."
Having an intermediate ability to stop someone from commenting for a short time has seemed like a good idea in the past, and continues to be something that isn't unworthy of consideration, but it's the the moderator silenced me but not everyone else aspect of this that I don't like.
For a suspension, a conversation happens - you're told precisely why the suspension is in place and have an opportunity to communicate with the moderator privately regarding context and circumstances. Since taking comments away from someone is essentially quieting them, I'd really like the escalation to be to a point where that conversation can happen, hence it's better to just go to a suspension if a moderator positively must stop someone from commenting.
In other words, I don't want to yank comment abilities manually without some kind of messaging happening - it might seem like it's subtle enough for many cases but I worry how much it might cause folks to escalate even more. And if you're going to message, you .. well .. might as well just be issuing a suspension.
It's not a horrible idea, it just stands to inadvertently make situations worse instead of calmer in the face of hot-headed dynamics :)