Translations don't work!
Comment forms are custom post types, they are dynamic content. You can have many forms for different post types and we allow you to change form title and field names as you want. It's not possible with PO/MO files. PO/MO files are not dynamic. There are only 3-5 phrase in comment form. Other phrases (99%) comes from PO/Mo files. For example the subscription drop-down options come from PO/MO files. If they are not translated it means your language translation files are not complete. You can update them using POT file and PoEdit program. wpDiscuz POT file is located in /wpdiscuz/languages/ directory.