I could be imagining this, but I'm pretty sure I joined MetaFilter twice. Back in early 2000, it was quite easy for every single blogger in the UK to fit in a reasonably-sized pub, and for there to be a list of every blogger in the world on just a long page. So I must have found Metafilter from somewhere like kottke.org or camworld.org
The first time I saw it, I suspect my reaction was 'Pshaw! How is this supposed to work, a community weblog? Won't everyone just post a bunch of random crap?' - but I signed up (I believe) looked around, and then disappeared. It wasn't until another few weeks that I returned and saw that not only was it still alive, but it was being actively used, so I signed up again using my real name and kept going.
A couple of years later in 2002, when Mefi had 14,000 users, I was sufficiently invested to write a blog post called 'The Decline of Metafilter', joining the grand, decades-long tradition of 'this site went to shit just after I signed up'. So it must be freaking awful by now.
How to Say Thank You
This thread: How to say thank you from 2003*. Could there be a better example of the collaborative hilarity, one-upmanship, snark, and good-naturedness of the Metafilter community? Probably, but I don't know what it is.
*There's probably something earlier, but shit - I joined Metafilter 11 years ago, how am I supposed to remember any more?