Surely though, it's not really 'acceptable' in a serious bit of research. Because you should be able to look up the references given, and decide for yourself whether they're believable or reputable. You (potentially) can't do that if the person you're quoting is using a pseudonym, because you won't be able to track them down. I don't know why people use pseudonyms on tma, but whyever they do it, it is of course acceptable within this kind of setting. But if their opinions are being quoted in a paper that's trying to set out The Facts, then personally I would want to have their real names. That's not so weird, is it? Otherwise you might as well say "a little bird told me" and invent all sorts of stuff that backs up your claims, citing (Little Bird, 2002).