Nevermind. For some reason, I thought they had separate logins, but upon further investigation, I realized they do use the same user login, but they just have different profiles.

Either way, I have decided to disable the K2 login/user forms and pages, and for the "article comments", I have simply added an "Extra Field" that says "Discuss This", which I manually link to a specific forum post. Not quite what I wanted, but I suppose I can fine tune the bells and whistles at a later date.