Eric's been on the team for along time. Almost all of the TF2 updates announced via HLDS had his name in the end for a good 2-2.5 years now. I don't know Dave though. Then we have people like John McDonald (who did OS X stuff) who was a new addition to the team with Gun Mettle, and apparently there's another John on the team who replied to my email regarding the crashes related to prop lightmaps. That's the first time in the 5 years I've been playing that anyone from Valve has replied to an email I sent via the Valve email website thing.
Again, my hopes for the game are on the rise again, after EotL made that hope completely disappear. Now if they manage to make this game behave memory-wise on OS X I'll be happy. Although I do wish the devs would read these forums more often and stay around longer. That reply by The Jill was a one-off, same with the post made on SPUF about the competitive TF2 group Valve made. I have no idea if my (or anybody else's) replies are being read.