I know you are working on better “contacts” functionality and groups etc, so this might be unnecessary to add, but sins I can’t find that it has been mentioned anywhere else:
If using special characters in any contact field (any field when creating new contact), this is possible to save with no errors, and appears to work just fine in the contacts menu. When exiting the contacts menu and returning to the web mail, then returning back into the contacts menu, all the special characters have turned into gibberish. This includes special characters in the email field, witch should prompt an error on its own.
p.s. I can not seem to find a way to delete contacts.
p.s.s. I no longer get error messages when trying to create folders with special characters in them, they just don’t appear. Same goes for too long folder names. No add blocker/ghostery active.