In my real life, only the restaurant or hotel waiter will call me "Sir".
I am wondering why many people here always use the word "Sir". Do they know that other person must be a man instead of a woman?
The most important thing is that we are all netizens，forum username is better. but call someone  “Sir” will only be treated as waiter by others.
In my opinion, calling someone "Mr." is not a kind of respect, but an inferiority.
Everyone is equal here, so avoid using the word “Sir”.