There's so much great about Mumsnet but then there's some stuff that just seems to be about making new people feel stupid or not included
That's a ridiculous attitude. There are in-jokes, there are abbreviations, there are all kinds of things that go on that not everyone is in on, old or new. Of course the longer you are here, and the more you post, the more you 'get' them, like anywhere else in life... you can't expect hundreds of people to act as though everyone is new all of the time just so someone doesn't feel 'left out' not knowing why something is so funny??!!