I dont think this place is cliquey at all.
There is however, an in-crowd. This is envitable, some of use have been here a long time, and have history before that, and have met on several, some many occasions.
The in-crowd also make this place what it is....4466 members, probably 50 very regular contributors, and another few hundred occasional posters. So there is obviously going to be a bit of a reportie between the regulars.
That said, it is by no means a closed group.
As for posts being ignored, I have been aware of one or 2, what I have noticed is if a 'newbie' posts a joke, that noone finds funny, it would tend to get ignored, rather than a load of get your coat type replies a regular would get, but that is surely being polite to someone you don't know?
Also at the meets, I have seen 'unknowns' being made very welcome, with only one exception to that rule of a member who was trying to attend with 2 parties and had a conflict of interest, and was upset the entire oof wouldnt join his other party.
I have also 1st hand seen what happens when a newbie is treated like a regular, with an innocent double entendre that was taken completely the wrong way, which could have easily been resolved, but quickly turned into a big deal.
other things that could make this place appear unwelcoming is the abrubt way newbies are told of their wrongdoing, I know some are obviously just trying it on to try and make a sale, but there are countless "Fill in your profile" requests, when a "If you put some details about yourself in your profile, it will really help us diagnose you problem, you may even find a local member offers to help" would be much friendlier. This is the internet after all, we are all well aware of the warnings about not revealing personal info, so people may well be reluctant to comply to such a 'demand' from a bunch of strangersm, however good our intentions are.