This occured to me after I watched the series on YouTube: Ghostwriter is basically described as having no senses apart from his ability to recognize written words, meaning that he can't see, hear, smell, etc. Sometimes the gang has him help track down the offender of the week by asking them to look for words that are near that person. (For example, they use this technique to find the name of the person dressing as "Stoop Dude" in "Into The Comics".) If Ghostwriter is unable to tell what the person looks like, sounds like, and so on, then how does he know whether he's actually anywhere near them when he reads certain words?
This actually does get explained in the first story arc. One of the kids (can't remember who) asks Ghostwriter how he is able to locate them if he can't see them. Ghostwriter explains that he senses their heart. Despite sounding sappy, it would seem Ghostwriter has some kind of empathic ability. He can locate people, but isn't able to see them in the same way that normal humans do.
Who is Ghostwriter anyway? How come he was never revealed at all during the course of the show? I mean, he can type almost any kind of words on the computer, but why not who he really was? I know some clues to his identity: He used to be a man, he was alive WAY before Walt Disney and Elvis ever became famous, and that he used to be chased by dogs. That's pretty much all I know about him. I know the saying "the magic is in the mystery", but why didn't he reveal himself to his friends in the first place by typing?
He couldn't remember his life as a human though the end of the show suggested that he was starting to recall some things (like being chased by dogs). The show probably would have revealed his identity eventually but was cancelled before they could. This troper has suggested that he was Jamal's ancestor who was an escaped slave (explaining the being chased by dogs thing).
He is, in fact, an escaped slave, as explained in a 2010 interview. He was killed while teaching other escaped slaves to read. Whether he's Jamal's ancestor is left up for debate, although that's the most likely explanation.