This came up on #lesswrong IRC channel, it was not a hypothetical future problem at all.

Being discussed somewhere does not show it is real. Personally, 'people are cycling from account to account to evade karma limits' doesn't seem like a real problem...

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).

Ah, cool!

Then, I have much less to complain about, offers of help are much more useful than suggestions from back seat drivers :)