According to the Yslow developers, even thse replies could be made far mor cache friendly by using the correct headers, especially by removing the ETags-header

According to the Yslow developers, even thse replies could be made far mor cache friendly by using the correct headers, especially by removing the ETags-header that forces a conditional GET on every acccess and replacing it with an Expires-header in the far future that allows to reuse the cached version without server interaction (assuming the images are not meant to be highly dynamic, then ETags would make sense). So from a caching perspective, HN has got it exactly backwards: it doesn't use ETags on the dynamic pages, where it might help, but uses it on the static content, where it might be detrimental. But I wouldn't bet on the gains you'll get from fixing this to be measurable.