This odd online persona can be intimidating when first encountered. When you're entering the forum as a newbie, you'll notice this person's name, signature and/or handle all over the place. They're one of the main debaters, they've planted a few Epileptic Trees in their time, and their knowledge of the forum's series/topic is second only to that of the Fount Of Knowledge.
But they've not spoken to you once in the month since you joined the forum. When you posted your introductory message, they didn't even reply with a one word "Hello." When you replied to their post, they ignored it, replying to the two regular members who posted before and after you. They don't seem to know you exist.
Oh, wait a minute — they have spoken to you once. So they must know you exist, because they made some rather acerbic remarks when you asked a question about the first episode (the Font Of Knowledge answered that one), or when you wanted to know which forum to post fanfiction under (The Shepherd bailed you out there). Something along the lines of "How can any real fan not know that?" or "Isn't it obvious?" if memory serves. Not the most positive feedback in the world. Provided you're not disheartened enough to leave the forum, you'll probably ignore the negative remarks, thank the people who did help you, and continue to learn the ropes of the forum.
Then something strange happens. As the newbie gets better acquainted with the fandom, starts taking part in discussions and gets to know the other forum members, they'll find that this character starts to warm up to them. They start posting replies to the newbie's questions. They ask for their opinions. Eventually, they're chatting away as if they've known each other for years.
What happened? Well, the newbie stopped being a newbie and moved up a rank.
Once a newbie becomes a valuable sparring partner/ally/source of fanfic, fanart or information, this character becomes much more approachable. You see it's not that (s)he's nasty — (s)he just Suffers Newbies Poorly.
They don't intend to scare the new blood off (guess who's in charge of that?), but they find the more obvious questions (and initial blunders) made by newbies intensely irritating. In their opinion, if you haven't got something intelligent to add to the debate, you should just stay quiet. They have next to no patience, and it doesn't seem to occur to them that not everyone who joins the forum is a die-hard fan with encyclopaedic knowledge of the topic. They conveniently forget that they themselves were the newcomer at some point. Still, once won over, they're probably one of the friendliest and most active members of the board. Their bark really is worse than their bite, as most of the forum will be quick to reassure you. The fact that this character is usually pretty well liked among the regulars and old guard of the forum is testimony to that.
Despite not being genuinely nasty, this is one of the few online personas that clash with The Shepherd, since the Shepherd patiently mentors the same newbies that drives Suffers Newbies Poorly bonkers.
This can also apply to games, where the person in question, rather than ignoring the newbie was a forum goer, doesn't help at all in a game. If it's online they ignore the "peon" and actively avoid anything that could get them stuck with this annoying new player or refuse to give tips or help to the newbie as they should be able to get out of it if they deserve their respect, for single player games they refuse to give help, saying "it should be obvious to a skilled player" or "Figure It Out Yourself" if they deign to reply at all.
For in online games, if it's a game where skill counts just as much or more than levels (such as online shooters or other action games), it can be justified as there may be reasons for not joining up with somebody who might not be as skilled and thus mess up their own game. This puts them right with the forumgoers in terms of attitude, but if levels mean more than somebody's reaction time and button mashing (most World of Warcraft-inspired MMO systems can be this), they can easily come off as jerkish and elitist, because helping them would seem to not be as risky on their part. Goes Up to Eleven in MOBA games such as Defense of the Ancients: All-Stars, though slightly more understandably, as a newbie's tendency to die early and often not only holds them and their team back, it advances the other team, giving them extra gold and experience. This can create a nasty Catch-22 Dilemma where in order to be beneficial to teams and not incur your teammates' wrath, you have to be good, but to be good, you have to play and practice with your teams.
As a side note about the above, newbies are most often subjected to this in game for not understanding the Metagame rather than other reasons. This can mix with any time of the listed above, but MOBA games are most prone to needing metagame knowledge due to the fact that practicing on one's own is harder.