I'd argue that HN got better after they hid the karma (net of 1 + up - down) on a per-comment basis (even though I was initially opposed to the change at the time).
They can still use like/dislike metrics to decide which videos to offer you and in what sort order, so there's still some signal available.
IMO, HN's fade is worse than just showing the like/dislike ratio. I believe some users see a faded comment and subconsciously get a preference to hit the downvote before even fully reading a comment.
Imagine if Youtube automatically showed unpopular videos in a permanently faded mode; this would be even more user-hostile.
Just give the users the count or ratio, and let them interpret (or ignore) it.
They can still use like/dislike metrics to decide which videos to offer you and in what sort order, so there's still some signal available.