Technically it wasn't "in" Valve. Rumour is the map was produced by the community, only that the guy got hired around the time the map went official.
Even then, "hired" is a loose term. Most people under Valve work on multiple projects under multiple roles; concept artists, modellers, Source coders, level designers, etc. Level designers also have a tendency to only work temporarily at Valve. If you look at the level designer list in the credits you'll find a vast majority of the level design team don't have perminant positions at Valve HQ and work for several companies on several games including mirrors edge, crysis, quake etc.
Phil Co is one such individual who has been working the level design scene since Doom and has worked for Valve on numerous occasions and is credited in several HL2 based mods, including the singleplayer. But doesn't actually work for Valve.
It's one of the things that has me concerned about under taking Level Design as a potential career path. I know many people here dream about working for Valve but it's way more competitive than most people realise. You'll find many environments across multiple big titles were created by only a few senior designers. It's made me realise the market potential isn't as big as we like to naively believe. A whole bunch of us here just make levels and have fun but very few take it seriously enough to do real world research on this kind of thing. If only a few senior level designers can get work for several companies on several games at a time, it's incredibly competitive, even if it's still a growing industry.
My only question at the moment is on whether junior level designers are actually getting credited on such big titles. Junior positions should be plenty available if that's the case. It's something i've been considering emailing valve about.
