There's a CSS rule on pre code that sets a max-height of 500px. This means that when you're scrolling through a topic, you also have to scroll through sub-elements to see all the content. To me, this is annoying enough on a desktop browser, but it can be particularly tedious and surprising on a mobile phone.
Does anyone else think that this is important behavior to maintain? Could the CSS on this forum be customized to get rid of that max-height constraint?
I agree. On mobile, I frequently find myself hunting for a sliver of non-pre code area so I can scroll the post rather than the code example I might not be interested in.
Third option: maybe keep the max-height, but disable scrolling within the <pre>, and add a button below that increases the max-height by 700px.
(I don't know how easy this is technically. But I'm sure a lot of other forums would also benefit from it.)
I like bgeronns suggestion. Give them a max-size with a button to see all of it. That way they don't interfere with scrolling and you can still see the whole code if you want to
Same here, the "nested" scrolling on mobile can be quite annoying.
I'm not sure if taking away the max-height (i.e. always fully expanding the code blocks) is the correct solution though...
It would simply collapse all the currently-nested scrollbars into one huge scrollbar for the entire topic. Basically, We'd always have to scroll the entire post; no more "slivers of non-pre" to hunt for 
A "show all" button as bgeron suggests seems like a great solution, combining the best of both worlds: limited height to scroll past in the normal case, and full scrollability (using the standard "whole-topic" scrollbar) on-demand.