I don't dress with specific clothing to LOOK like a commuter, but being one, I probably fit the clothing "stereotype"; sans the lycra since I'm a Clyde.

Having said the above, I have noticed a major difference in attitude (more courteous) when I ride with pannier, helmets and high-viz clothing.
And having spoken to colleagues at work who don't cycle, they tend to be more "forgiving" to cyclist which look the part of the commuter than random people riding with dark clothes and/or without lighting or helmets.