Quite interesting question : as a recent user of MO, under the pseudo "Smaug", I'm not presently perfectly aware of all the guidelines and "good behaviour" rules.
For me, MO is a quite nice meeting spot, due to the variety of its content,the easy and informal way of asking and answering, and, above all, the evident courtesy of most (but not all...) of its members. So, why do I use this stupid pseudo of "Smaug, Dragon-King under the Mountain" instead of my equally stupid real name ("Jean-Marc Patin, undergrad math teacher in Nantes University, south of Brittany, France) ?
For a quite simple reason : it helps me not to take myself too seriously and not to make too much of my mathematical preoccupations.
I've got absolutely no interest in "advertising my brand", it should be clear that I'm a somewhat real person (even if I've sometimes got nagging doubts about it), I definitely do not consider myself as a mathematician (while beeing aware that most MO members are true ones), but I'm quite proud to be a math teacher, and I fail to see what damage can be done by my (possibly stupid) questions and my (possibly dumb) answers. So I do believe that returning to the (relative) anonymity of "Smaug" is harmless, and certainly not offensive.
After all, "Anonymity", "Courtesy", and "Pertinence" are probably three independant random variables...
Please, feel free to savagely down-vote this answer. Yours truly.