I rode in work slacks last week for a 40k ride... I was expecting some problems as I'm normally in chamois-padded bike shorts but it was fine. I did go commando to avoid any underpants rubbing so perhaps that was a factor. The seat is a cheap POS too. I am well-padded subcutaneously FWIW

I also used to commute 10k each way in work clothes and clipless shoes and didn't find any problems.