Found out the problem. There’s a rule that says:
#content img {
...
width: auto
}
This causes images scaled via HTML attributes to be overridden to the image’s real size. In all fairness, HTML attributes for height and width are deprecated, but I can’t imagine it was intentionally broken.
Removing the line that says “width: auto” doesn’t break anything that I can see, because “auto” is an image’s default behavior anyhow.
