As this thread demonstrates, there are a lot of reasons for calling someone sir or ma'am and whether you do depends on what it means to you. I personally don't care what other people call each other, in chat or wherever, but I assume a lot of the sirring in chat is just flirting and I don't see anything wrong with that. I looked in on chat one time a while ago and someone was stirring up drinks and serving them around the room, but I didn't worry that people were going to drive home drunk. It's just for fun.
For myself, I find titles at the wrong time to be distancing. I'll very occasionally use one for fun, or to make a point, but when I'm serious I find that using a title that doesn't reflect my real feelings doesn't deepen the experience but trivializes it.