I received a message that the icons for unread vs. read posts are so similar that they look the same to colorblind users. I quickly replaced the "unread" icons with images from a different design ("milky way"), and that helped. However, the new images weren't the same size, so it looked a bit odd together with the rest of the original images ("prosilver").
I've now replaced the imageset once more. The site now uses the original design "prosilver" but with the complete imageset from "KS_Serious", so we're not mixing imagesets anymore. I've tested the new imageset for colorless contrast and I'm satisfied with this look, but I'm always open to additional feedback.
If you see any problems, please send me feedback. Either send me PM or post here. I'll see it either way and work on a solution!