In the "Additional Link Parameters" on the "Edit Link" screen, special characters are escaped when you save. If you go back and edit that link, the escaped characters will be escaped again when you save the changes. So you have to "un-escape" special characters every time you edit a link, otherwise you accumulate the "\" character before each instance of special characters.
Perhaps this is part of the "Link" functionality and not specific to Link Library. But, if not, it would be great if the system checked whether special characters are already escaped instead of re-escaping them.