I remember when Yahtzee was just a random poster at the Home of the Underdogs forums.
Unkillable Cat and
rezaf will probably remember as well. He stayed true to his nickname throughout.
There was no other social media back then, and AFAIK that was the only place where he promoted his stuff when he first started out.
He started with a website that had the tagline "Where laughter goes to die". I remember thinking that the guy has talent back then, there was some really funny stuff on it. Also, the tagline was just great, which is why I remember it. It was one of the very few "random website by a random guy" (which was basically all websites back then) that I visited regularly. Unfortunately I can't remember the url, I'd like to look at it on archive.org. IIRC HotU putting his first game "Six days a stranger" on its front page was the only promotion he ever got.
He also got his first girlfriend from the forums and they moved in together, but they separated shortly before he got his job at the Escapist.