Currently CoAuthors_Plus::get_coauthor_by() fails to retrieve guest authors whose "user_login" names contains non-ascii characters. Those user_logins are effectively slugs so they are stored in the database url-encoded, and thus should be compared against a url-encoded version of the user_login if they are to be found.
Currently CoAuthors_Plus::get_coauthor_by() fails to retrieve guest authors whose "user_login" names contains non-ascii characters. Those user_logins are effectively slugs so they are stored in the database url-encoded, and thus should be compared against a url-encoded version of the user_login if they are to be found.