1. The thing I now dislike about HN are the posts that get upvoted. Yes, eternal September and all, but this has persisted through the slower summer months and I don't see it ever returning to the high S/N ratio of the recent past. I find myself more often finding gems on pages 3+ with top posts just being a general feed.

2. Discussions are now becoming rare. So many posts sit on the front page with many upvotes and zero comments.

3. Downvote misuse as mentioned is irksome but not fatal. My problem with them is the UI for them. Upvote if you agree, so downvote symmetrically (and incorrectly) implies disagree. Downvote should really be represented as 'flag' with a type such as factually incorrect, disruptive, adding nothing to the discussion, or other poor conduct (as mentioned in other replies regarding the guidelines).