Just bear in mind 408.21 is fairly new. It may not have been adopted when the house was built.
Greg, while that is true, it’s my understanding the compliance with UL67 for panel boards has always been that way.
Don’t forget to do the robot walk.
Calling this as a 110.3 is not as common as one would expect and it is very likely that you would see double lugged neutrals before the 2002 code made it clear it was illegal. It was very common to see the ground and neutral for a particular circuit under one lug.
I write it up either way, and I do indeed tell my clients that this issue is todays standards.
That is the luxury of your job. You are just there to voice concerns, not to enforce code. A code inspector can’t really complain about things like light switches behind doors and receptacles in inconvenient places as long as they meet code. You are there for the buyer.
Personally I don’t see double lugged neutrals as a huge concern until harry homeowner starts poking around in the panel but it could be an indicator of unlicensed/unpermitted work in a newer home.