These guys are even more paranoid than many smaller instances about user names that appear to be randomly generated. Your own user name, as others in this thread suggested, would easily trigger their auto-ban rules. And a human moderator would take one look at the name and think the same thing.
God damnit, it took me until now to actually read their username. It's the youtube URL for the rickroll video (ending in XcQ). I think you're right though - it was obviously autogenerated originally and only took on its current meaning via Youtube's use of the string.
The problem is scaling. If it takes say, 30 seconds per name, but the number of n is very large, then if you ban say, 1000 dudes a day then the 30,000 seconds becomes a requirement of 8 hours of mod explanations (collectively) per day. It's a scaling issue, in short.