@Molot brought up a point that I found deeply flawed and so I am moving the ideas here to better address why I have a concern over that policy.
I've posted the commentary below to provide context.
Frankly the "No longer needed" reason should ONLY be used if the OP being commented on addressed the comment. However, having one of my own comments deleted using that flag sometimes feels like an act of suppression against opposing viewpoints so that they post can continue to get positive/negative votes without others seeing the comment that would otherwise invalidate it. – mkinson
@mkinson if OP is not going to use your comment, then it is no longer needed. Stack is not a discussion forum. If you have an opposite view about the answer, what you really should do is to post your answer, and downvote the one you think is wrong. With questions, close votes, downvotes and flags, whatever appropriate, are way to go. Comments are not for presenting your viewpoint, so if you feel deleting comments oppresses your viewpoint, then you are using them wrong in the first place. Use them only to improve post you are commenting on, please. – Mołot
@Molot Doesn't that go counter to the idea that people want a comment when a post is down-voted? If a moderator removes a comment to a post and that comment addresses why the post was down-voted I am certain the poster would appreciate seeing it. – mkinson
@mkinson No. If reason for downvote is something OP can and might want to fix, then comment is a good thing. But OP is free to ignore it, and then comment no longer serves any purpose (again: not a forum!) and should be removed, because it is no longer needed for anything, go write your own answer if you can do better. Trying to force your idea into someone else's post is a bad form. – Mołot
Answers to Questions should use factual evidence when possible, and clearly stated. However, there are times when someone’s view on a “fact” can be shaped by their own beliefs and internal bias, and because of that the presentation of that “fact” is flawed. The suggestion that the comments are not for presenting a viewpoint and that addressing those flaws should be handled within your own post has two major setbacks. The first is that your post will likely get flagged as off topic, and the second is that a post with incorrect information is allowed to continue presenting itself as factual when it is not.
Comments should absolutely address posts directly with opposing viewpoints, because that’s how we are able to promote critical thinking in others who are reading the post for the first time. If you block opposing viewpoints because the comment section is “not a forum” then you’re effectively suppressing dissent and promoting opinion over fact, which fundamentally goes against the spirit of why this site was created.