That is interesting. I happened to notice that some described ligatures under Dutch aren't appearing for me for some reason. I've been thinking about font rendering in different scripts lately since I like the DejaVu fonts but unfortunately the project was abandoned a while ago and coverage is incomplete in many areas. With other more complete fonts available these days it seems likely to be better to use a more restricted version of the fonts to allow fallback to the more complete scripts, although I'm not sure how well the unicode blocks match actual usage. It is easier than ever to mix languages but still hard to know if you are messing them up. I found out my terminal was rendering Japanese wrong when someone posted this link recently:
