[jcynix]

Credit card numbers come to mind, printed in letters they are often grouped into four number block separated by whitespace, e.g. "5432 7890 6543 4365" and now try to copy-paste this into a form field of "length" 16.

Ok, that's more of a usability issue and many front end developers seem to be rather disconnected from the real world. Phone number entry is an even worse case, but I digress ...

[zinekeller]

The UK Government (at least those based in GDS) has noted it (https://design-system.service.gov.uk/patterns/payment-card-d...), but some definitely are not good here. Also, hypens (or dashes) aren't popular in the US but (somewhat) popular in the UK!