The Address Book's contacts' Other Attributes' values take XML entities (& < > " ') as input, sometimes requiring them to display text correctly.
I can verify this in Claws Mail veresion 4.0.0 under Kubuntu 22.04 LTS. Also, when the & < > " ' characters are used in the Value of Other Attributes, the Value is ignored and is replaced by the Name of the Other Attribute until you replace them with the XML entities.