comments on vendor dashboard

Are you referring to the vendor dashboard from the Frontend Submissions extension?

yes

Note: all support for commercial EDD extensions needs to be handled via https://easydigitaldownloads.com/support – This is due to rules on www.ads-software.com that do not permit us to discuss commercial plugins here.

I will go ahead and see if I can resolve the issue for you here, however.

To disable the FES comments tab, you will need to apply a custom code snippet to your site. Are you comfortable doing that?