@aruseus493 First, congratulations. You won the Most Misleading Topic Title of the Week Award thanks to "dark" and "leveling" in context of edgy RPG-style novel.
As for actual concerns, it's not likely to be caused by clipping (I doubt JNC would ever adjust colors unless assets they got were in a very wrong range or something). Here's a less bad screenshot from an app (with some extra scaling because of device's resolution and extra JPEG artifacts thanks to imgur)
Histogram here almost gradually falls near zero while clipping usually causes a peak with nothing after it (like here on 255, but that's kinda intentional). The first peak is are pixels with value of 10 and those are shadowed part of image. To make something disappear in that background you'd need to clip everything below 10 which would make lots of other lines disappear as well.
The loss of detail is caused by some combination of downscaling, JPEG compression, possibly denoising, and your screen being unable to show dark colors well.