Joseph,
All I was saying is that it is a two way street. It is uncomfortable for a regular to find someone in their seat, and it is not nice to ask someone to move. It is also uncomfortable for guests who are unsure where to sit, and it is not nice for a guest to assume and cause others to be in an uncomfortable situation as well.
No, gabbaim do not wear name tags, nor should they. Basic decency says that a new face shows up in shul, someone should go over and welcome him and offer him a seat. since this discussion assumes we are not on that level, the next step down is causing an uncomfortable situation and dealing with one.