Where can I get a comment service?

Question

Blogs

It is necessary to raise the service for blog comments.
Requirements (from non-obvious ones):
- tree-like (at least 5 levels)
- authorization via Oauth2 and OpenID (LJ)
- voting (+/-)
- sorting branches by rating
- decent load (500,000 views per day)
- good statistics on commentators
- notifications of new replies to commentators by mail
A third-party service will do, but I doubt that there is one. Obvious disqus and hypercomments don't fit entirely. It would be better to find something ready for your server.
According to technology, some Nodejs + mongodb is asking here ...

Answer 1

if you need a ready-made solution, then here:
https://github.com/posativ/isso - python
there are various third-party services, in addition to disqus there are also IntenseDebate, Livefyre, etc. (the last two definitely have tree-like comments). The main advantage of such things is spam protection, less hassle to support this.
ps You have very interesting views on the choice of technologies. mongodb is no better than mysql for this task.