You believe everything Spike says?
Like I mention in my notes above (artist comments are for reading!) the chip thingie is something Spike would probably like to keep mentioning, in this whole "post-canon" comic setting which is presumably after his whole story has played out - it gives him a plausible excuse to hang out with good guys, for which he did kinda acquire a taste (... not literally), and an ace up his sleeve to play in a tight spot when people think him powerless. Also, is kind of his more unique trait. Yanno. There are sparkly vampires, and angsty soulled vampires, and the chipped vampire...