Thank you for the link!
However, my (motivated, I admit) reading of that text is that Eliezer wants to bring attention to a paradox of downvoting a comment and discussing below the comment. Either the comment is an interesting discussion-starter, and then it should not be downvoted; or the comment is worthless, and then people should not start a discussion below it. Downvoting a comment and discussing below it is kind of supporting something you oppose.
If it's a seriously misguided but good-faith comment by a newbie, I might want to downvote it and explain why I did it. Hanlon's razor.
I just found out that a new website feature was implemented 2 days ago. If a comment is voted to -4 or below, it and all replies and downstream comments from it will be hidden from Recent Comments, and further replies in that subthread will incur 5 karma points penalty. The hiding, but not karma penalty, applies retroactively to comments in that subthread posted before the -4 vote.
This seems to be worth a discussion post since most people are probably still voting things to below -3 without knowing the new consequences of doing so.