While the ridiculously low contrast of downvoted comments is a problem, let's say for a second that "you're meant to ignore it anyway, and we use low contrast to indicate it" is a reasonable idea. Then why is the main submission text lower contrast than the comments?!
I think the main text has a higher contrast than downvoted comments?… I’m mot sure, actually. If they receive lots of downvotes, their text colour becomes really pale.