Can you be more specific on what you think the problem is?

I agree that the current (downvoting + minimum karma for Discussion) dynamic encourages creating new accounts, holding everything else equal. But I'm not sure what the downside of inflated registered-user numbers is - there's not much sock-puppetry locally, so it isn't clear how additional registrations can be considered relevant to signal-to-noise issues.

And there are tangible benefits to the downvoting system (helps increase quality posts, crowd-sourcing basic moderation).