The HN website can do what they want but it seems anti-democratic to muzzle opinions and debate by making comment box text unreadable making the text colour lighter, just because some people (a few downvoters) find the words uncomfortable.
On the contrary, the community decided that text is not worth reading. It's very democratic. If enough disagree with the downvotes they can upvote the comment and make it black again.
If you can read it you may upvote it but often you, I know I often do/did, will just breeze over it and ignore it.