Maybe there's some logic I'm unaware of but we're allowed special characters on other pages but on the Product Page

Sorry, validation failed for your request

Field: Name Plural

You can only set alpha numeric characters 'A-Z', 'a-z', '0-9', spaces, and these characters . : + - / ! % ' in the field 'NamePlural'.

You can get round it by saving it without and saving again with, but it's a time drain.