Another example is https://maps.wikimedia.org/osm/18/156717/106651.png .
I'm not sure what the deal is. Clearly it can render Hebrew, and Max's example also shows it can at least sometimes render Arabic.
After an IRL debugging of Hebrew labels with Stas and Ori, we narrowed it to Mapnik going bonkers from some combinations of 2-byte and 1-byte UTF. Minimal repro: "א-" - that's aleph and minus sign.