If you follow meta, you have seen considerable discussion lately regarding comment deletion. Usually comments are deleted because they are obsolete, off topic, impolite, or have turned into noise (long, extended discussions that detract from the actual post).
Normally, this deletion goes on quietly behind the scenes so that you, our community, do not get bogged down in the tedium of moderator actions. However, I thought I'd try to get some community consensus on this process.
The type of comments that we normally delete:
"So true / +1 Excellent question!" / "I had never thought of this before." / [insert funny comment]
Noise: These types of comments are pure noise. We usually let them stick around for a few days while the question develops, but there's little need to keep them around in the archives since they simply takes up real-estate on the screen.
"Could you add a reference?" / "Don't forget Mark 97:32!" / "How does this address X?"
Obsolete: These are comments that tend to go obsolete after a post has been edited. We know that these are obsolete because they're often followed up with "Good point. I added that to my post!"
"Well, what about X?" / "If you believe that, you must believe X"
Off topic: Discussions that take place in comments can sometimes add to and improve a post. However, most of the time, they tend to be off topic. Comments about slavery (for example) on a question about stealing are clearly off topic and tend to get removed.
Non-Constructive: Comments are intended to be used to help improve a question or an answer. The way Stack Exchange is architected, comments are meant to be very temporary in nature. Because of this built-in architecture, they tend to be poor places for extended discussions. Therefore, the moderators (both voluntary and SE employees) tend to remove extended discussions after a certain point and direct people to the chat room (since chat is more permanent, more immediate, and intended for long discussions).
Our ideal is that these types of comments would be automatically cleaned up by their posters. However, we're all human and we tend to forget sometimes that something has been resolved or we tend to get carried away and forget to move to chat.
So our question is, how else can we help the community understand comment cleanup?
In addition, would you the community be willing to flag such comments left by others that are obsolete, chatty, or not constructive for us to clean up?