I believe Spike wears the same suit in Tabula Rasa. I think that scene is about Xander's own insecurity within the group. His own father is not a great role model (as we see in Season 6 and hear about throughout the show), and Giles is the only other older male that Xander has regular contact with. It could suggest that he wants Giles to take on the father role, to embrace him like a son, and instead Giles is giving all that to Spike. Xander subconsciously feels so unloved by his father that he feels like he's not good enough, therefore the man he wants to be a father figure (Giles) is overlooking him as well in favour of a soulless vampire.Do you think that Spike in a suit with Giles as watchers have any signification ?