T126825 fixed the FOUC on mobile however if you visit https://en.m.wikipedia.org/wiki/Los_Angeles_Lakers on a desktop device and scroll down.
The sections are initially collapsed but expand as soon as the JS loads.
e.g. loading the above on an (emulated) average 2G connection in Chrome (54.0.2840.98) looks as follows:
 Test that there is no FOUC on mobile
 Test that there is no FOUC on tablet
== Suggested Solution
A media query should be introduced to override this while the JS is still loading.