> I know that these "+1" aren't entirely useless in that they show support - but people can show support by other means, and on other websites (for example, by simply upvoting the HN submission).
That's not linked to or visible from Github, and assumes the repository owner watches HN or reddit or what have you.
Other systems have ways to simply note that you're affected by an issue without having to spam it, but Github has nothing for that: subscriptions to a bug thread are (AFAIK) not available to the repository owner, and there's no "+1" button, the only way to show interest or that you're affected is a bump comment. Which admittedly isn't nice, but how else is the repository owner going to know this issue affects more than just one person living in a cave on a lost island in the middle of the pacific? Issues are not treated based solely on their "popularity" or on the number of people they affect, but that's an important signal when prioritising.
> Maybe a feature to fold nonconstructive comments would be the solution - but how to determine which ones are nonconstructive?
Repository owners can remove comments, FWIW. Of course unless they also lock the thread that will most likely lead to an avalanche of now outraged claims of censorship.