this harkens back to my BBS days, and I realize that my feelings on this topic are largely considered unreasonable, but it's just the way I am. Deal.
If someone wanted to be called Fred in these type of forums, then that person would have chosen Fred as his/her psuedonym when signing up (unless such a name was taken, but I'll not get into specifics). If this person choose, instead, B33rM31st3r as his/her psudeonym then we owe that person at least the minor level of courtesy to use that name when referring to or adressing him/her.
It just seems to me a matter of respect. Some nyms are, arguably, too complex or difficult to type and as such shortening them to a reasonable nickname is expected and a reasonable compramize. In the situation where the nym is not unreasonably long, complex, difficult to spell, or offensive, however, why is it so hard to use it?
Just my thoughts. Feel free to ignore them.