Our most recent thinking about this (ref. Ellie’s comments) is that peer review may be too onerous an activity to expect all validators to do this on a regular basis. However, ref. a proposed validator code of conduct on Cosmos Hub https://github.com/hyphacoop/cosmos-hub-charter/issues/3, it might be reasonable to initiate peer review upon a norm breach or CoC violation, which then results in some sort of penalty (e.g. withholding foundation or Commons delegation to that validator). This way it’s not a centralized entity enforcing norms.