It was just a polite remember that there is a patch to be applied to
ploticus source on WMF servers (no answer from upstream, looks to ignore
me :( ). Doing it while the custom builds of ImageMagick and Rsvg looked
as the reasonable thing.
The patch won't magically fix the already broken pages (the generated
files seem to not be deleted on page edit) but will stop that source of
invalid XHTML.
There's also a patch pending for the php code, but it's lower priority
as a sysadmin is not needed for it (in fact, it was fixed and reverted).