Ah, that would makes sense. Happens to me all the time when I leave HN pages open for a while then try to use them later. I imagine the bots try to follow links they picked up earlier a long time later as well at times. Kind of funny a bad session system on a site can kill your search rankings, though. It would be fatal for sites that live off Google traffic, and tough for people using off the shelf software to deal with.

Specifically your no longer ranking for your main brand! That's nothing to do with your long tail search terms.

It's NEVER been an issue before this time with consistent top results for years and this suggests otherwise https://www.google.co.uk/search?q=site:news.ycombinator.com&...

Btw this is showing the pages indexed for the site HN. That its not showing in the results now for your brand WILL have devastating results on your traffic directly from Google. Though you might not care?