If you enable the dark theme and have the "Show captured pieces" preference set, any captured black pieces are invisible against the dark background of the page.
well it depends which piece set you use. Which one do you use?
Second piece set (my favourite) has captured black pieces indistinguishable from the dark background. It works fine with the first piece set, but I'd much rather prefer the second.
Yes, I was going to make a thread about the same issue. It's still possible to possible to discern the captured black pieces that have white highlights on them, but the pawns lack any white highlights at all. I would use the third or fifth piece sets as a workaround but I find them too difficult to read quickly on the board.