I thought it would be the memory segmentation system introduced by the 286 processor: https://en.wikipedia.org/wiki/Segment_descriptor & https://en.wikipedia.org/wiki/Global_Descriptor_Table

There was a lot of unusual things back then; now I think memory is flat so your stack address 1234 is the same as your code and data address 1234 (the exception being thread-local variables).

I thought it might have been about Feature Descriptors like SIFT/HOG/ORB from Computer Vision

You all jest, but I'd kill for curated tags on HN. There's a lot of content here I don't really care about and it's steadily growing larger. Nothing wrong with the site, just personal preferences.

I wouldn't kill, but probably pay for an app that builds that on top of HN.

I wouldn't hand-curate the tags, but parsing a well-commented HN discussion, or the fine article under discussion, might lead to hints. For instance, given a Title term "Matrix", one might parse for "movie", "mathematics", "transformation", "neo", "algebra", "agent smith" and discover to which tag "matrix-movie" or "matrix-math" the discussion should be assigned.

Adding a UI that presents the tags in the Algolia search might be the difficult-to-get-right part.

I guess classification via combination of article and comments shouldn't be too hard (at least in my imagination). I would like to subscribe to tag-based RSS feeds then, ideally.

Did you just invent subreddits?

No, why? I'm talking of automatic classification with multiple tags per post on top of a random mix of topics as we have it here.

This wasn't about Win32 SECURITY_DESCRIPTOR s? I thought not. Though, Win32 security is indeed hard, and I'm diving into assembling and debugging security descriptor ACLs right now...