I assume this is directed at least in part toward me. Including thread history below the reply is Gmail's built-in behavior. If there were a setting to change that, I'd be more than happy to use it, but as far as I know it's not possible to change that default. I can do my best to remember to manually remove the collapsed copy of earlier messages, but I have to be realistic that email is a habitual workflow.
In my humble (and I'm guessing unpopular) opinion, collapsing reply history included below an email reply is an expected UI feature given that every email system these days needs to handle messages sent from Gmail.
