That top search result thing is probably the real story here, not the 10,000 number. Boards like that get indexed hard by Google, so once a thread has enough replies and age on it, it floats to the top for stuff like "vapor barrier under slab" and then it just sits there pulling in strangers for years. I bet your 47 messages didn't all come from the milestone post at all, some of them probably found you through a thread you wrote back in 2019 and only now decided to message instead of lurk. The scary part is you can't edit a wrong answer out of search results easily, so if one of those old posts has a half right take buried in it, you're now the unpaid help desk for it forever. There's a name for this, it's the reason some guys stop posting, they get tired of being quoted like a book they never meant to write. Ten thousand posts is a lot but the milestone just gave people a reason to hit send on questions they were already sitting on.