And I just remembered about this bug by chance. Was looking at rsvg-bench, and how the libreoffice icons are much bigger/slower than other icons. Then I looked at one in EOG, and it was wrong. Then I looked at it in rsvg-view, and it was okay.
So I remembered about a bug I had seen in Bugzilla a long time ago... and there it was, with a proposed fix since two years ago.
Kids, do bug triage. #fail