You can already do that for them by creating multiple vBComments profiles, and setting the user permissions for the profiles to match the users you want to have access for.
Unless you are using one user account (i.e. News System) for your vBComments posts, you'll have to create a profile for them to post as their username in each of the forums you want them to be able to post to. (i.e. vB DraX in News; vB DraX in Community; vB DraX in Support)
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