Static title translation problem
In this file:
There are two functions called getHeaderTextSingle() and getHeaderTextSingle()
These function contain static word "Comment" or "Comments" that are used in the comments form, but they are not translated to other languages.
Please make sure these static words can be translated via the "Phrases" options.
Those phrases can be found and translated from the Dashboard > wpDiscuz > Forms admin page. Just edit the Form and find Comment form header text (singular) and Comment form header text (plural) fields.