In this comment on Subscription DAOs, it says that BMAIN managers can earn up to a 3% bonus of tokens each epoch based on their participation as judged by other managers.
Since voting is limited to the first 50% of managers who vote, rather than participation being measured only by a race to vote, we can also measure contributions to discussions on topics relevant to the DAO. Such discussions often precede votes in a healthy DAO.
The platform used is up to the creator of the discussion, but discussions should legitimize and draw attention to each other by cross-linking. Cross-linking between discussions avoids centralization of control of the discussions.