@user21820 It would be helpful if in future someone (e.g. you, as you brought the post to the attention of CRUDE) pointed out the error of the answerer. Especially in this sort of question, where the user has written a lengthy answer and appears confused by the downvotes.
(by reading the comments to the question and one of the other answers, I think I've worked out the issue. But it would have been much easier if I didn't have to do that...)
By the way, about the above issue, I should say two things: (1) user1729's parenthetical remark is precisely the kind of confusion of students that can be avoided by simply ensuring that they do not see the misleading post. (2) I pinged specific users who have the expertise (in logic) to review that post correctly. It also ensures that if I or others make a mistake they can rectify it by voting to undelete and telling me why I am wrong.
@user1729: See above. (You weren't in the room just now that's why I used the 3rd-person.)
@user21820 I think pinging relevant users is sensible, but just saying "see comments on other questions for an explanation of why this is an incorrect and misleading answer" is not a big effort, and would have saved me some time...
@XanderHenderson @amWhy @Holo @JoséCarlosSantos @AlexFrancisco: This answer is wrong for the reasons already given in the comment, and should be deleted.
Next time, @RushabhMehta, don't answer in the comments on a poor PSQ that turns out to be a duplicate. You answered another question earlier today, very poor question, in the comments. Don't do that, else the users will post more crap hoping to get an answer, in a comment, like you offered, or in an answer.
@amWhy I usually just like to give a bit of a lead (which I do in comments) but then close the question. I do that so I'm not farming rep, but at least the poor souls have a direction to look at
I thought the point of closing questions is to clean up the site
I can stop giving skeletons of answers in comments if you think its counterproductive, but I tend to like it because I feel like as a community, we tend to both alienate a bunch of clueless math users while also having to deal with a bunch of PSQs
@RushabhMehta And to create no incentive whatsoever for users to post crap on this site in the first place. Yet you've provided such incentive anyway. "Why shouldn't I post a crappy question? I'll get an answer in an answer, or in a comment, which is what I'm looking for. Do my work for me... and I'm happy."
@amWhy I guess that's fair, there's a balance to be struck. In my personal life, I've just found that I rather have people who ask bad questions than none at all, a problem which I think has alienated a lot of Americans from math
@RushabhMehta I'm not suggesting you do it for self gain. That I realize is not your goal. But it still reinforces helpless "do it for me" behavior on the part of askers.
@RushabhMehta But you'll find there will be answerers who do so anyway, and they'll restate exactly what you stated, if it's been upvoted. That's been my experience commenting, anyway.
@RushabhMehta strictly hints can make good comments. I'm not saying never help in a comment, but try to do so below questions in which askers made an effort, even if wrong. In my mind, I will never penalize a wrong attempt, or a partly wrong attempt, if it's a sincere attempt. Below posts like that, hint, comment, or answer to your heart's delight! :-)
@RushabhMehta Closed (hammered)!
@RushabhMehta (I know you've seen this, just wanted to link to it for: ) @XanderHenderson This is a dupe of at least five other posts.