Of the many people you've met (both irl and online) through the making of this wondrous game we call Dominion, who do you think has had the biggest effect on how the game has evolved over time?
The people who have affected the game the most are all in the credits, no surprise there.
In the early days, which mattered the most, Dame Josephine, then Dame Molly, then Sir Destry. I mean they were the ones playing every week (or twice or more a week for the dames). And Dame Josephine had to listen to me talking about the game when we weren't playing. I didn't meet them through making the game though.
During development, we can add Valerie and for all I know Dale, since they did work on the game and the game was changed due to her/their suggestions; plus my original online playtesters (using my own program which did not have internet support - we played over aim), including Sir Michael (especially for later, he didn't play much at first), plus Sir Vander, who did not play so much but chatted about the game. Post-release, some other playtesters have been notable, especially John Vogel and Bill Barksdale (sorry I couldn't knight you guys). The early playtester credits include a bunch of "people who got to play the game before it was released," which is to say, sorry guys, I really did not get much out of you and I am not sufficiently polite not to say it, although at least I'm not naming names. Later credits just have the people who really contributed and well they all did, you had to contribute extra to make the credits. Anyway again, I didn't really meet most of the playtesters through Dominion, I already knew them. Or met them but not through Dominion, just because they were playing games in the same place that I was playtesting.
So, if we stick to "that you met through Dominion," then Valerie, for all I know Dale (I put it like that because stuff came from Valerie), and hey, Jay. Alchemy got pushed forward and smallified because of some mix of Jay, HiG, and Schmidt-Spiele. Intrigue didn't have colored treasure coins because of some mix of partners. And the promos exist because of the people who wanted them, Spielbox etc. I haven't even met those people. Dark Ages isn't War because of HiG.
The game itself had that pile of expansions in various states before being released; there was a lot of balancing for playtesters to work on, but "how the game has evolved over time?" There was no evolution except better testing, so there was no-one to affect that evolution.
Who has had the biggest effect on how the community has evolved over time?
I'm not sure if you mean dominionstrategy or something broader. Man I don't think I can give much of an answer either way. Ask the community! Jay has had tournaments and got the game on BSW; Doug made isotropic. Theory / Frisk / Renaud started this place.