Just create multiple accounts. Hooray!

Any system can be gamed by the determined. Luckily, most people are not that determined.

But we're talking about designing new systems to reduce the influence of people who are ridiculously active. These people aren't quite determined by definition, but they're the best candidates for "that determined".

That arrow doesn't go both ways.

Even if the most determined to cheat people are highly active, I don't think most of the highly active posters are determined to cheat. I think cheaters are a tiny proportion of users.

If people keep creating new accounts, they can't gain any reputation or other social linkages. No karma, no name recognition, nobody knows it's the same person. No continuity, not even a conversation.

Even if new accounts are easy to make, I think that would be unattractive to most people, who are simply participating and happen to post more than others, not being malicious or trying to cheat in any way.

For the few trolls, and advertisers trying to subvert the feed, a different mechanism is needed to keep those down to a manageable level, as has always been the case.