Since I haven’t done my Lost review this week, I’ll post a comment I made on a forum.
I don’t think Walt ever typed anything on the computer. I think it was in Michael’s mind. I think Walt was trying to communicate telepathically and couldn’t get it quite right which is why he was visible to Shannon and Sayid but his speech was backwards. He found it easier to project the typed text into Michael’s mind.
When Jack walked in on Michael after Michael had been talking to Walt on the computer, the screen was blank although Michael did not touch the keyboard and only a second later had been in mid-sentence with Walt.
I think Fake Henry is a strong telepath. Remember Jack saying “you’ve got good ears.” He wasn’t listening through the door. I think when Michael came into the hatch, Henry finally found a mind weak enough to control. Henry, not Michael, shot the drunks, er, I mean examples, er, partiers, er, no, um, ladies…yes, Henry shot the ladies.
I still think that when Henry said to Anna Lucia, “you killed two good people” that he was looking into her mind and referring to incidents off the island.