When it's been rainy and muddy, my feather-legged birds do get dirty foot feathers, but they otherwise keep them clean, and with one exception (mud balls that like to harden to the tips of their long foot feathers), it always dries and flakes off of them like with the clean-legged birds once the mud has tamed down. I suspect if my coop was not in such a bad location for drainage that they would have no issues keeping them clean, but as it is there is constantly mud just outside the coop door whenever we have a lot of rain.
My Cochins in my breeding coops don't have issues with that, however, because they are housed in pens that don't get significant mud. They always have lovely, clean foot feathering. Pristine, as RoyalChick put it!
I don't buy into the whole 'chickens picking on an individual for them looking different' thing, or the 'birds of a feather' thing that a lot of people say happens with chickens. Having had chickens since childhood, nearly two decades now, and only occasionally having more than a few individuals of each breed in all that time up until recently, I have never noticed a significant amount of segregation or bullying by appearance. The only time that I have seen any kind of bullying because of a visual trait was less because of how the bird looked and more because that trait blocked the victim's ability to see the attacker coming; for example, Polish of
any color are very often the victims of these cases--and very often can't see anything but their own feet because of their huge crests.
I think it has more to do with temperaments of the birds than with appearances, personally. One of the most bullied birds I have owned did not look significantly different than other birds in the flock at the time, she's just a very meek individual in general and got pushed around a lot when she was younger. So as far as that goes, I would not worry about appearances so much (except for large crests) and look more into the breed's reputation for temperament. Especially coming into an established flock as a newcomer, I could see some of the bearded breeds with a reputation for being very docile and gentle, like Silkies and Faverolles, being the victim of bullying. Your good ol' standard bearded Easter-eggers tend toward being less meek and more bold, and mine get along great in a mixed flock of various temperaments.
Just my two cents there, though.