How do I see a user's full post history?

So, here's the thing. I tend to follow specific people on these forums, just scrolling through their stuff. But lately, when I go to check someone's post history, it’s acting weird. It only shows me a limited number of posts from certain dates instead of everything they've ever written. For anyone with more than 300 posts, the list just cuts off, so I can't see anything before those first 300 entries...

If I actually wanted to read every single one of their posts, what am I supposed to do?

Not really.

But if you want to get specific, you can actually filter a user's posts within a single thread. Just look at the top right corner of the topic, click "Search this topic," and then hit "Advanced Search." It’s a bit clunky, but it works.