From the submitted blog post:
"I have a suggestion for improvement: it should cost Karma to comment, and when your Karma drops below a certain threshold you can no longer comment.
"My reasoning is that the trash comments we all hate are kneejerk criticisms with little thought put into them, which I suspect are largely made for the sake of saying something and collecting Karma."
I agree with the rationale for the proposal here. The bad comments are the comments that pg described in 2011
http://news.ycombinator.com/item?id=2403696
as "comments that are (a) mean and/or (b) dumb that (c) get massively upvoted."
No one should be upvoting a comment that the current author refers to as "trash comments [that] are kneejerk criticisms with little thought put into them" because such comments fit the definition of comments that are both mean and dumb. If you see something that is mean, absolutely downvote it. It's clear that our site founder and most veteran members of the HN community (and all of the most thoughtful members here, however recently they have joined) don't want any meanness or kneejerk criticisms here, so download comments like that ruthlessly. That's upholding the guidelines.
Dealing with comments that are dumb (in pg's words) or have little thought put into them (the OP's words) is a bit harder, because if I don't have domain-specific knowledge, I may not know what comments are dumb. Wikipedia has its own problems with lots of dumb content, so often looking it up on Wikipedia will only add stupidity to HN. But in threads about subjects I know about, I try to scan for comments that point to reliable sources (that issue is crucial) and otherwise show signs of thoughtful research before posting. Then I upvote comments that I know for sure to be polite, true, and informative (well, I try to do that routinely here anyhow) and I downvote comments that are shown to be dumb by the context of the discussion and reliable knowledge of the world.
We can all do the same, if we can upvote or downvote at all. Some users with accumulated karma can also flag comments that violate the site guidelines.
http://ycombinator.com/newsguidelines.html
(To flag a comment, follow the "link" link text next to the comment, which takes you to the specific URL for the comment, and there you will see a "flag" link if flagging is enabled for your user account.)
Basically, every moderation problem on every forum (I have been a forum moderation on one forum or another since 1993) involves someone being willing to take out the trash. It stinks to have to take out the trash, but someone has to do it. If you have upvoting power, upvote the good. If you have downvote power, definitely downvote the mean ("kneejerk criticism") and downvote the dumb ("thoughtless") to the degree you can identify it. If you have flagging power, go to the extra effort of comment-specific flagging for the especially bad comments. But most of all, upvote the good. I have a slogan that I tell my children to help develop their social skills that "no one ever receives enough appreciation." So be generous in upvoting good comments, to drown out the bad.
And thanks for agreeing with pg's statement from last year
http://news.ycombinator.com/item?id=2403696
that both comments that are (a) mean and comments that are (b) dumb shouldn't gain karma, but rather lose it.
P.S. I see from the other comments in this thread that there is confusion about whether the original blog post, which has the title "A proposal for improving HN - it should cost Karma to comment" is about submissions of new articles or about comments to submissions by others. That appears to be related to the submission title here, which is "A proposal for improving HN : it should cost a user Karma to post" as I type this about an hour after the blog post was submitted as a new submission here on HN. I am only talking about comment rules in my reply here, not about submission of new article rules.