Grammarly for Knowledge - AI that recalls useful information from your notes, messages, and docs.

You mean Memex (Vannevar Bush)? Still waiting for a good implementation of that one. If you find something, I'd like to know. Along those lines I use !Diigo for keeping highlights/notes from web reading (it also works with PDFs, can import Kindle highlights, etc. but I rarely use these...the experience isn't smooth enough). Unfortunately the service hasn't seen a lot of enhancements recently but still a pretty solid product. I also tried !Memex for a bit, haven't tried it recently. They have seem pretty big aspirations (per their name). !Raindrop is another useful one for link knowledge management. I'm also aspiring to build a next-gen web search engine that would handle web knowledge management - nextsearchengine.com. Theoretically it could provide a complete public knowledge management system - but I haven't planned anything for private knowledge management. Finally, I use Markdown for a lot of my notes. Keep it in a git repo. Can be pretty powerfully searched using Visual Studio Code or similar editor. I really like markdown. There are a few products out there that organize and link markdown docs but I haven't played around with any of them too much (yet). Obsidian is one I think.

no, that sounds really cool though and I'd like to know if you find (or build!) anything like that. If it worked well, that sounds like it could be a game-changer for humanity, really. I typically throw things into Evernote and keep in mind the rough idea of what's in there for my future reference. Or, if it's more important, I physically write it down to have it stick in my brain more, and/or put an alarm or calendar note on it so that I don't forget whenever I know I'll have to reference that again.