We are trying to modify the plugin functionality. We don't find any hook or filter to disable the comment form for a specific user.
If we add a filter here then we can achieve what we want.
You should add the custom code in the theme template files and not call the comments_template() function for the current user.
We have some user permission system. Some users can post only public comments and some can post only private comments. We need a way to hide the comment form only from specific users. So the users can't see the submission form but can see the comments. If I follow your suggestion then the whole comment system will be hidden which is not the thing we want.
I do know that I can achieve by following your suggestion. In our case we need a way to to hide the form programmatically. If we have a filter in the line that I showed, we can do that easily without modifying the wpdiscuz plugin.