Certificate transparency is a permissioned blockchain (a merkle hash tree), ran by a group of trusted organizations and observed by third party monitors ("validators"). Your browser probably queried that blockchain when you opened hackernews.

It's a Merkle hash tree.

You can call that a blockchain if you want, but we already have a much older and more specific term for it: Merkle hash tree.

Sure, I just wanted to point out that building merkle hash trees, or blockchains, or whatever you want to call it, isn't "all rubbish". There are some valid use cases.

My point was that people who talk about blockchain typically refer to something other than a Merkle hash tree - they refer to a hash tree plus some consensus mechanism for trustless addition. I don't know of a term other than "blockchain" that can be used to refer to this concept.

It doesn’t even have to be trustless, some of this crap is using RAFT (for speed), the assumption being that the participants are all trusted.

the blockchain is just a database. a database timed and validated by block. After all a database has advantages / constraints.