Why is it not mandatory to provide comments on a down-vote?
Some questions can be unclear, and most users are nice enough to leave a comment on the question to let OP know what needs to be fixed to either get an answer or to receive a better answer.
However, I've been noticing lately that answers to questions have been getting downvotes with no reasonable explanation. And not all of these answers being downvoted were bad at all. These answers were what OP was asking for, except in different words than other answers on a same question; that is how this site works. (These answers were, for the most part, valid; just not OP's preference.)
Then, I've been noticing lately that questions are no longer receiving helpful comments for question improvement. Instead, they are being downvoted without giving OP some direction as to what can be said differently in the question.
I've quickly looked through meta to see if there had already been a question like this, and I did, but in the sense that other users were being harassed by downvotes.
Combining with what I've seen happening with unexplained downvoting of answers and questions and then reading what was linked above, that leads me to this question: Should downvotes require comments to let the user know why their question or answer is being marked down?
I'd further like to note, that here on meta, someone was confused regarding their own question in 'Main', and had to ask in meta to find out why the downvotes happened. Another case, is right in this link.
Once again, I really want to ask:
If you are downvoting, should you have to comment and give a reason why? (I'm wording the question differently so there is no confusion as to what I am asking.)
When you downvote, you are requested to give a comment to let OP, or the user who was answering, know your reasoning. Everyone doesn't do this though. Sometimes, there is a user who gave a reason saying something along the lines of '-1 no research' or '-1 not constructive'... something like that... There are multitudes of downvotes and that particular comment to the downvoted question gets upped. I find that okay because it is leading the user or OP to realize that people agree with the comment. As with not commenting at all, not everyone does this upped-comment of '-1'.
In case a flag for possible duplicate: I found this on meta as well, however, it is different in the sense that the OP was thinking about more guidance for downvoting, whereas I would prefer there being a mandatory comment needed to be given for a downvote.
If we expect questions to be constructive and on-topic, shouldn't we expect the same thing from those who are voting? Wouldn't it be constructive to let OP / answering user know what was wrong with the question / answer?
Should downvotes require comments?