I don't think I can outdo Miss Dio and Miss Emilly (and see the links therein) (edit 1/28 1:00 p.m.: and now the colorful Mr. Antfarm) on this subject, so I'll keep this entry fairly short. It's fine for the Lab That Dare Not Speak Its Name to provide the option to link publicly an avatar name with a typist name, but absolutely out of the question to require such a link.
I can imagine cases where a user would want to create voluntarily such a link, although every one that comes to mind involves commerce, where potential customers feel more confident about doing business with someone whose "real" identity is known and verified. (The scare quotes around real are there because it can't be all that difficult to fake a real identity, so one's level of confidence in the other end of the transaction is not 100%. And, shocking as it may seem, not everyone is honest, even if his identity is known.)
On the other hand, many people, including Yours Truly, have personal and professional reasons to keep the two worlds as separate as possible. Mr. Galactic Baroque, commenting on Miss Orr's piece, noted that complete separation was difficult, if not impossible, in an age where comments made via the Aether were available and searchable, and while true enough, for the most part it's not worth the search effort. (Lesson: don't do anything while under an online alias that pisses off someone so much that the search effort costs less than the reward of finding out a real name and acting on that information.) Others have pointed to concerns over allowing the Crazy Stalker type to know a real name, or email address, which can be used to carry out Crazy Stalking activity to one's person. Sister Kathy told me a story the other day: in-world, she met and began conversing with a woman who revealed that she had turned down a (virtual) marriage proposal. The rejected swain started behaving erratically, at one point asking the woman for her (real) email address. Thank goodness for the wall of anonymity, no matter how crumbling that wall may be!
Good reasons, all. Ultimately, though, I don't find those reasons to be as compelling as the one that Mr. JJ Drinkwater masterfully summarized in his comment to Miss Orr: "JJ Drinkwater is a story Boswell [his typist] is telling. But, in some rich sense, we are to be known by the stories we are able to tell, are we not?" Indeed. Those stories may be silly or profound, written down or extant only as they occur, but they are separate from the teller of those tales. The authorial "I" does not live in the Steamlands and have adventures there; Rhianon Jameson does.
Most of us have mundane existences. I know I do. (Not that I'm really complaining. There's a reason that "may you live in interesting times" is a curse.) If anything, I would prefer that Rhianon show herself in the real world, not that her typist arrive in Caledon. Failing that, let me keep them separate.