Google them??
Seriously. Google maintains public archives.
Background: I actually just ran into the same issue & drew the conclusion (confirmed by @babowa) that Apple was applying a pretty aggressive chronological filter (😒). Fortunately, I also had an idea re: workaround solution, which I was amused to discover did seem to work. Granted, mine is an extremely limited test case (I had a grand total of 2 inaccessible mystery Qs), but a fundamentally similar approach should work for you.
The Simple (if inelegant) Solution: I queried my username + ‘apple discussions’ @ google.com. They were actually the top two hits in my search results.😁
Fair Warning: Assuming we’re fairly likeminded, this solution is probably not going to be super-satisfying. You’ll probably encounter some technical challenges with the search algorithm to recover a much larger sample set of 150ish historical posts. Even if you do manage to excavate all your old posts, it won’t generate a very tidy record of your activity. 😕
Bottom Line: All that said, if you rate a semi-functional workaround as better than nothing, this should work. 🍀
Follow up: Feel free to. I’m curious to know if/how well this works for your larger sample set. Or if you find an alternate/better solution.