TL;DR I'm famous and contributed to the Python community, I'm depressed (it's real! Check this references) because people don't like me forcing them to use my tool. these people must be awful.
Java is compile to bytecode which is then interpreted by a virtual machine, it's not compiled to native code, that's why you cannot distribute Java programs as executable like go.
It's been like this forever, the police have access to so called "information management system" directly to QQ and later Wechat. There is no other way to talk to people online, you are monitored in all channels. They have no choice, anyone that doesn't cooperate is blocked. Also the sense of "Privacy" is very weak among Chinese, they are brain washed enough to believe "what are you afraid of if you have nothing to hide". So yeah people will continue to use Wechat and other social channels in China.
Yes, it's very impressive, and the purpose of the whole post IMO is part of the marketing (call me evil). Also if he didn't quit his job, he probably wouldn't be able to get this far within a year.
There is no where they mentioned "replace nashorn", the main feature of nashorn is to interoperate with Java, V8 cannot do that. If you follow the development of Nashorn, they are working on ES6 features right now.
Also replace nashorn with V8 simply is a false statement, V8 is of it's own project established before Nashorn, and it doesn't even belong to Oracle, how can one replace a new project with an old one?
What? Where did they say that in that talk? They simply showed a way to execute native code with V8, so it's easier to run node on nashorn. Stop spreading misinformation.
A concurrent map in my understanding, is a map that can be accessed concurrently without explicit synchronization, not each coroutine has a piece of it. Check java ConcurrentHashMap.