Also, since altoid directly posted a link to the Silk Road, I would guess (not sure) that Ulbricht argued in his court case that it wasn't actually his account. Maybe he wouldn't want to contradict his past testimony?
Ulricht
declined to testify in his defense. His lawyer may have argued that point in court, but that is not the same as his own testimony.
I am guessing that he probably wants to move on from the Silk Road chapter of his life. I doubt he has much interest in posting from an account that he spent very little time using.