We can wear flip flops on Fridays. Plus, it's super hot here, so I will take what I can get. I think it depends on the office atmosphere, and the industry you are in. Just because you work in an office, doesn't mean it's a lawyer's office, or some stuffy corporate office. For instance, a lawyer's office is probably going too have a different dress code than a construction office.
I guess I really don't pay enough attention to study someone's feet. There are tons of fashion no-no's that can be seen at any office on any given day - muffin top, panty lines, ill fitting clothes, bad hair cuts, etc. Even a peep toe or strappy sandal, which are professional, still expose your feet. I know you are strongly against funky feet, so have an idea for ya - stop looking at them ;-p