I don't think its fair for you to say that you have no choice but to act a certain way London. You act one way with your family and then you act another with clients. But, its the way that clients treat you that will determine your behavior in return.
BTW, that's not a bad thing either. So, don't read anything into it.
But, to the question of topic.......
Everyone acts big, tough, knowitall, etc. behind a computer. Some do it because they can't be that way in real life, some do it because its just the way they are. But, the board persona the people have is usually an extention of their real life.
What I type is me, take it or leave it. I speak my mind and usually say what others think and wish they could say, but are afraid of doing so. Sometimes I say it the right way, other times I say it the wrong way. I make mistakes just like everyone else.
Do I come across as bitchy on the board, sometimes. But, I can come across as bitchy in real life too because I refuse to be a doormat. I am the best friend a person could have once we get to know each other and will give the shirt off my back for you if you needed it. I like to joke around and have fun. Too much of the board starts to jade a personality.
I have yet to see or meet one person who comes across as the perfect board member, they don't exist.