Reader mode doesn't work on all websites
For example this forum right there:
At night the contrast gets really unpleasant to read at night (even with F.lux installed). I tried to see if it will work better (than before there was a built-in reader and I relied on extensions) and I found out that the button is missing.
@LAMBDA471 - It is not possible, due to the way reader modes and extensions are designed, for them to work on all websites. Developers have to make decisions in design to a) get correct detection of which sites will render properly in reader, and b) how to detect elements and make changes in them to make reader work.
Different readers and extensions work on different sites, some work on more sites, some on less. There is no 100% reader code.
Generally reader view doesn't work on forums, and when it works it will usually only show the first post. The code works well for blog posts and articles, big passages of text and suchlike. That's the same for all the readability extensions out there. Someone mentioned that reader view is going to improve over the coming months, but I think it won't ever work on this specific website. You should look into extensions like Stylish to change the look of websites individually.
I guess my only solution would to edit the colors in Inspect more. Thanks.