Of course intrinsically it is not. But if it means you look less professional than everybody else competing for the spots, I wouldn't advise it. I'm sure it's inconsequential in 99/100 cases, but what if you are that 100th case and some old fart on the committee was turned off by your attire and votes to reject? My whole point is that you just never know--why risk it for the sake of making a moral stand against conformity? (and it's not like khakis, a button-down shirt, and loafers is much more comfortable in the first place.)