I've never considered this question before.
I agree being anonymous means you can be more open, but I am well aware I have a tendency to want to be liked, so I am not likely to be rude, brusque or anything like that here in the virtual world or in the real world. Very occasionally my halo slips and I say something I immediately regret - and then apologise.
I have to be careful and remember that not everyone is my friend. I do struggle with the forthright manner of some posters because it doesn't feel right to me, but that's my problem not theirs. I've always been opinionated and spent my working life in support/advisor roles, so it's natural to me to suggest what someone can do even if they never asked!
But there's a difference for me between GN and the other online places I post. I learn a lot from being a member of GN. There's such a huge range of life experiences here, partly because of the age of the members - basically from about 50 and upwards - half a century of living in some cases. I'm at the younger end with no children/grandchildren and only one of my close friends had children (child actually). Despite how heated discussions can become, I love the way on GN we can talk about anything and share our opinions. I'm sure the anonymity aspect gives lots of posters the chance to discuss subjects in a way not available to them in real life.
As much as I enjoy posting here, I suspect I get more from reading posts than writing them.