Yes. It might sound a little backwards but it can be done by disabling comments. The process would be something like
1. In Admin>Posting, untick "allow comments on answers" and same for questions.
2. Set up language files in qa-lang/en (or whatever your language is). See http://docs.question2answer.org/translate/ for a guide.
3. In the new language files, change "Answer" to "Comment" where applicable. (Change the value of each element in the array, not the key.) For example in qa-lang-main.php the first line would read
'1_answer' => '1 comment',
4. Add whatever CSS styling you need to make it look more like comments. You might need to fiddle with some other options regarding voting and such too.
Now people will post what the system thinks is answers, but on the front end they appear to be comments.