You're still allowed to reply to their post quotes from the article that make it clear that they didn't read the article. I've also just done the "I know it's against the rules but did you read the article?" thing in the past. Haven't gotten banned yet.
"Did you even read the article" is a cheap shot that commenters routinely take at each other. It has nothing to do with the topic at hand, so it adds noise, not signal. Since it's a putdown, it provokes others and degrades discussion. If you take out the cheap shot and preserve the correcting information, the comment becomes better in every way.
You can think of it as a special case of this rule: When disagreeing, please reply to the argument instead of calling names. "That is idiotic; 1 + 1 is 2, not 3" can be shortened to "1 + 1 is 2, not 3." But it's a special case worth singling out, because it's so common, and it's bad for HN in two ways: mean and predictable.
Right, but the idea here is that you shouldn't be allowed to comment until you've at least apprised yourself of the subject.
Of course, hiding a button with JavaScript is trivially defeated by your typical HN user, but I want to assume at least to some degree of good faith... this would be more of a "commitment device" than anything.