Wow, you became aware of Birkitt's character in 2005 (do you know Michael Jackson is still dead?). Smitty was appearing on The Late Show years before that time
Are you referring to Barbara Gaines, now the Executive Producer? She's a lesbian. Whether she was "out" going back to her days on the NBC show, I don't know, but I do know this: In June, before any details of actual sexual intercourse between Dave and his staffettes emerged, I remembered for the record Letterman groping Gaines on-camera.
Strange you should say that, because I vividly remember back in the NBC days how Letterman did EXACTLY that on camera.Dave used to do a bit in which he would call people at random from the White Pages from across the country (that's how he found Arnie Barnes, a "meat shaper" working at Omaha Steaks). Given the task of bringing the phone directories to his desk was Barbara Gaines, a production assistant. Gaines would enter from stage left and put the phone books on Dave's desk. As she would bend over and flip the pages and place her finger on a person selected to be called, a grinning Dave, while making idle chit-chat, would slowly reach behind her with his left hand. She would flinch and giggle and playfully say "C'mon!" or something.
At the time, Letterman was widely known to be dating writer Merrill Markoe, so it struck me as odd that he would be goosing a staff member on camera. Years later, Gaines, who eventually became Executive Producer, came out of the closet, making it more mysterious. Nevertheless, it happened that way, and wish I had video to prove it.