So answer to your comments SilentGhost:

I had a look at what Mozilla recommend. Their proposition of using position:sticky is interesting and probably possible for this use case but might require quite a bit of extra work. There is also the other suggestion to use something like https://lodash.com/docs/4.15.0#debounce but that would mean more jumpy animations but less computation. Also there is this http://caniuse.com/#feat=css-snappoints that would solve the issue created just before but it is not well supported yet.

All in all interesting points.

Off course I am willing to spend some time on optimization this if necessary. But before that I might want to have some kind of "approval" that my work as a chance to be used.

And I have a question for you R. David Murray. Look here for example:

https://docs.python.org/3/library/asyncio-protocol.html#udp-echo-server-protocol

What is the value of having an empty left sidebar here? Shoudn't we remove the sidebar completly if you have to scroll all the way up anyway? I don't really see the value for this sidebar in many of the long pages Python documentation offers.