Dark mode is good but it's hard to read the quote when it's on.
It's from a jr member so I am hesitant to use the script with account (even though it looks harmless on glance) but used without one and here are the impressions. 1) what do you mean with highlight op posts?
I can confirm that it does not work, but by reviewing the code, its purpose is to make the OP post color #ff9c59 font-weight: bold