>How should the developers of these clients feel certain that whatever alternative they decide to endorse won't end up like Voat?

Make sure the community has proper and sane moderators/admins and stamp that down before it flairs up. Because it's the internet, it will always flare up if unchecked.

But I get it, that involves trust in judgement, and the internet attracts some very zealous personalities that don't have that. You'd need someone with a proven record to champion that cause. I'm not sure who that is.