I am one of the downvoters to this post, and I'll add an answer.

I'm against this because I believe the bad far outweighs the good in this case, from long debates to users getting attacked etc. If you want to drop a comment yourself, please do.

Another problem, what if another downvoter already posted a comment? Does every other downvoter need to post a reason for the downvote?

Take the following old post on meta.SE, for example, https://meta.stackexchange.com/questions/272956/a-new-code-license-the-mit-this-time-with-attribution-required.

This post was downvoted 533 times as of this writing. Do you really want to read 533 comments to that post where most of them will be the same?

*I can also recommend checking the following posts https://meta.askubuntu.com/questions/linked/2008?lq=1 and their answers. Almost all of them are about the same subject with good discussions.*