[Zak]

This is something federation (e.g. Lemmy) solves, but it has its own signup fatigue that's higher than average.

OpenID with arbitrary providers aimed to solve this, but never took off. I think I only used it with Stackoverflow. Instead, we got OAuth with Facebook and Google being the only widely-accepted providers.

Layer a federated reputation system on top of OpenID and there could be a pretty robust anti-spam/asshole mechanism for independent forums and reduced signup fatigue.