In many states you are required to stop if a pedestrian is crossing the street. What has happened a lot is I will stop to let a pedestrian cross the street at a legal cross walk and the person behind me will assume I am an idiot, honk, and speed around me. My intuition is this is the cause of a significant amount of pedestrian deaths: impatient drivers that assume every stopped car is just an obstacle to zip around.…
I'm not sure what the penalty would be for overtaking a car stopped at a crossing. In theory it's the same, but in practise I think the stronger offence of dangerous driving would be used. If found guilty, that's an automatic ban from driving, an unlimited fine and up to 2 years jail.
It's so rare I can't find any news on this happening without other serious offences (speeding in residential areas, etc). I think it would count as "overtaking dangerously" though: https://www.police.uk/advice/advice-and-information/rs/road-...
The area you aren't allowed to stop within, or overtake within, is marked with zig-zag lines: https://www.highwaycodeuk.co.uk/pedestrian-crossings.html