I wasn’t even aware of beta.steemit or hives before you reached out to me, but after reading the comments I have one thought. While it might be useful to limit who can post to a tribe/hive/community, the nature of a blockchain is that is a public ledger so anyone should be able to examine anything on the chain. Perhaps the way to control both posting and reading access is to use a tribe/hive/community encryption key so that only those granted the key (probably over an external channel) can post to that tribe/hive/community by virtue of the fact that only they have the key to read it. Everyone can access the record on the blockchain, but it would be gibberish to them. Kind of like when I encounter a post in a foreign (to me) language ;)