So, this theory is fairly probably wrong, but it is possibly true and certainly interesting.
This forum is called the Seventeenth Shard because Brandon said so, according to the post A welcome to 17th Shard, and the rules. As I was recently reading the first letter, I came across a line that says
The author for this is probably Hoid, which leads me to believe perhaps some of the Hoid sightings in the book aren't actually Hoid. Again, I have no idea whether this has any grounding, but I enjoyed coming up with it.