It's Harlan, and he does read them regularly. I know you aren't used to that kind of open line communication coming from an AD since we were stuck with Woolard for so long, but I know he reads them, and I know he personally answers them on his phone. I have been in front of him when he's done it.
Working in intercollegiate sports, I can tell you most AD/Coach twitter feeds are run (for the majority) by an assistant and/or intern.
I'm not buying its always Harlan, nor am I buying that he reads all the tweets