This is just my personal opinion but in an online format such as this and the way I was trained "Sir" and "Ma'am" are signs of respect and unless I know someone here really really well using either of those negates the respect factor that I personally associate with the word. Therefore, I seldom use the titles and opt instead to be polite and use the person's id/name.

I haven't been in chat a lot lately but I don't know of many here who require "Sir" to be used. And none who expect to be called "Master" except by theirs. I do know of several Dommes who dislike the word "Ma'am" and will ask you not to use it.

Personally, someone I just met requiring me to use "Sir," "Ma'am," or "Master/Mistress" would send up HUGE red flags to me as to if they are even worthy of such honor.