The STW IT Support Collective (most posters here), along with the media world and most civil servants will shun any idea that what you look like on the outside may be taken as a reflection of what you are like on the inside. However, it is human nature to make some level of judgement (whether you like it or not) from appearances – it is how we learned to survive.
The t-shirt wearing types will make smart comments about ‘not being clever enough’ or ‘being judgemental’, but it is human nature. I dress differently at different times. If I am riding a bike, I won’t wear a suit. However, if I am in a meeting, I probably won’t wear lycra. Am I a slave to conformity, or do I know how to use human nature to my advantage? Your call.