Yeah, there's a big difference between coming into a job interview in Jedi robes or a Lord of the Rings Elf ensemble and something more subtle like that. When we had an unofficial Dr. Who day at my job one year, the only way I could tell the Ten cosplayers apart from any other patron was honestly the hair and occasional coat, and most of my coworkers didn't even realize they WERE cosplayers until I pointed it out.

Is it eccentric bordering on being weird and maybe not in the best taste for a job interview? Probably, though if it gives you a confidence boost when you're nervous I could see some people doing it. But it's a lot different to be in a suit or dress shirt and tie than going in your Final Fantasy or Star Trek getups.