Here's what the "comment everywhere" privilege page currently states:
When should I comment?
Comments are intended to:
- provide feedback on posts
- add relevant, but minor, information to posts (if it's a major chunk of information, it should be an answer!)
- ask for clarification or corrections
- discuss the content of the post with other community members
I'm not sure when this page was last updated, but some of this no longer seems to be good or constructive advice. The "official" network policy is that any extended discussion should be conducted through chat. It's now even enforced through the comment UI, wherein posting too many comments in a short enough period will trigger the message:
Please avoid extended discussions in comments. Would you like to automatically move this discussion to chat?
We also have updated comment flags for comments that are "too chatty" or "not constructive".
So specifically I have a problem with the guidelines:
discuss the content of the post with other community members. I have to assume that this advice predates chat, because we are actively trying to discourage "discussion" comments.
provide feedback on posts. While this isn't always bad advice, we have a real problem with the proliferation of meaningless, chatty "+1" comments - and that was identified as a problem even before we had chat.
Would it be OK to revise this section of the privileges page with more modern advice? If so, what would be good to put in it?
Some good starting points (IMO) would be the Programmers FAQ ("Can I use comments to discuss the topic of a post?") as well as the chart on Gardening.SE.