A serif humanist typeface for text

Pretty nifty. Question about the example at the bottom. There is "different" with an f, and then there is "different" with the "long s", which doesn't make sense as "disserent" is not a word.
@balupton I believe it is an example of the ligature support. If you are unfamiliar with ligatures, the Wikipedia article is actually a pretty interesting read:
@kleneway yeah sure, but it seems used incorrectly as ſ is the letter s, not the letter f