1/ The article doesn't claim to support one million concurrent users. Top level directives are Ubuntu/RHEL defaults, but if you have a preferred scalability config please file an issue!
2a/ buffering is well known to break SSE. As the article notes, if you're not using SSE you should disable that include.
2a/ buffering is well known to break SSE. As the article notes, if you're not using SSE you should disable that include.
2b/ I thought the config parser would have caught this but didn't. Filed https://github.com/certsimple/nginx-http2-load-balancing-con... and fixed.
3/ If you think your own DNS server is going to be better maintained than Google's, sure. But not everyone else would.