Iansf,
Why does it cause hostility in others?
Because shy people are quiet, they act as a potent mirrors for others.
What actually happens is that the person develops anxiety or feels threat or they mistake your quiteness for arrogance. They may think "this person doesnt like me, wont talk to me, whats wrong with me. So they engage you through their own insecurity by being hostile. Such acts of insecurity, we dont usually notice because we are too concentrated on our self.
As for chat rooms, the rule is simple. Posts are reflections of the state of mind that person is currently experiencing. They are literally engaging with their own reflection or a mentally conceived version of others. I wont go into detail as that isnt appropriate, however you can tell if someone is genuine and compassionate over time by reading that persons posts so then you can gauge if they are peaceful, loving, compassionate.
Try not to pay too much attention to the minds of others and what they think, its usually full of pain and suffering, that being said there is much to be learnt about them and of our own minds.
Did you perceive the message as 'scolding' because you were seeking approval?
Sometimes when we want approval, everything anyone says to us is sharply srutinized or not to our expectation, im not saying this is true for you but i just thought it was worth mentioning.
Compassionately,
Jack