@Baerrus there are no perfect examples, but while quite different, IPBoard 4.0 (beta) groups the posts "per pages" and allows easier navigation, clicking on the page number or arrows. While not perfect, this improves mobile navigation for long topics to some extent.
In what concerns to nodeBB the perfect solution in my opinion would be to put the "x out of y" post navigator right below the top "nodeBB" horizontal bar. It will take just a little bit of screen space while greatly improving navigation. No need to code new things, just some CSS tweaking.
Or a simple draggable scroll bar. Or at least an icon to go to the last post.