People are mostly just listing the names they've seen around a lot. They aren't applying much, if any, criteria for judging the influence of a person. You also have to consider how they contribute.
For example, until we made V a mod, he was mostly the forum's veteran comic relief and booster of morale -- generally not the most influential of positions as far as the site goes, although an important one for the community. Now he goes through the drudgery of cleaning up littles messes like bots and forums spats before most of us admins even see them, and without his work it'd be like when Gray disappeared all over again. He's become somewhat essential to the operation of the site, and what he says carries weight.
Furthermore, as the first form of moderation most newer members encounter on the site, he also has influence over the site by enforcing its norms -- if not shaping those norms in a very hands on way. And in a similar sense, he has also frequented a variety of Internet locales from time to time where he is sometimes the first person to spread knowledge of the Compendium. In that sense, he has influence over how other communities view ours.
However, long before that he used to be part of the founding analysis discussion of the site, and in that sense, he's been much more influential to the formation of the content on the site than many of the members who've joined in the last few years. Now that a new game means throwing some old theories out the window, that ship's sort of returned for a while, but you get the idea.
More so along those lines though, the only person who's maintained a direct role in the content of the site, the focus of the community, and the atmosphere of the forums throughout the entire lifetime of the Compendium has been Z. That's why he's considered the real founder of the site. He's even pro-actively reached out to other communities and is known to personally pop up in any discussion that even vaguely mentions the Compendium.
