Agree with you on all the rest, and I think writing a post like this was very much intended as a gut-check on things since the early days are hopefully the times when things can get fixed up.
The leaked Claude Code codebase was riddled with "concise", "do not add comments", "mimic codestyle", even an explicit "You should minimize output tokens as much as possible" etc. Btw, Claude Code uses a custom system prompt, not the leaked 24k claude.ai one.