Thanks. I'll need a bit to digest, but it looks like this will be super helpful. The ability of clients to quickly and efficiently filter out events that don't have a valid OTS timestamp (where "valid" means that they don't have an OTS timestamp that falls within a specified recency window after their created_at) should be a fundamental part of the Nostr protocol. It's about as important as the ability to filter out events that don't have a valid signature in the first place. I'll likely have questions after I've had a chance to think about your explanation ...