Personally I kinda enjoy reading the banter, trolling and such surrounding the buy/sell forum. Believe me there are plenty more (euro) forums where exactly the same thing happens.
The usual consensus is that a bike is overpriced and people tend to point out all the flaws, non original parts and such.
I don't see much wrong with that. I'm heavily I into shifty puchs and where I live there's a lot of people who don't now shit about them, find one in a shed, look at prices online and think they are going to get big bucks for it.
Some poor guy new to the hobby might fall for it and pay way to much. I don't see anything wrong with a few guys on a forum criticizing that. Its not like a few forum posts would stop the bike from being sold. Plenty of dumb suckers out there.
I guess it boils down to the fact that a lot of moped enthusiasts got into the hobby because they enjoy cheap crappy transportation and take themselves and their bikes not that seriously. I know I'm one. If prices become really inflated and the hobby becomes really serious naturally people are going to protest that.