I think the site has been down for a good couple of weeks now. usually it would go down for like 3 days this time is taking much longer.
As for the other questions I am not really the best person to answer them though:
- The impression I have for the documentation is that it is auto-generated somehow from Krita’s Cpp files. I think that is why it is so weird.
- As for autocomplete I came to not appreciate auto complete the more I coded so what I thought was a limitation when in Krita I just yeah I am neutral now and go by without it fine but it should be there for sure. Python in Krita has it a bit rough. I had a real hard time starting out because it is all locked in the Cpp files and that is a massive waste of my time going that route.
The best option you have now since libkis is down now is to use this plugin:
it will search your Krita and find all commands available but you have to guess what they do 
But this plugin should be featured somewhere and never is it is one of the best still.
Since your starting out if you see something like starting with “kis” or “ko” it does not exist in the Python API.