It just adds flavor to it. Makes it look like a weird document you would stumble upon while flipping through boxes in your grandfather's attic.
It's silly, but given how interesting the write up is, I find it pretty cool. It's always good to have something that deviates from the boring, ad infested, JS guzzling norms of web design.
It's fine for a monospaced font to contain an "fi" ligature (to represent Unicode U+FB01), but it absolutely should not contain a "liga" feature to form it from "f" and "i". I'd personally not even create a "dlig" (discretionary ligature).
Not surprising to see this, because the rules are quite different for non-monospaced fonts (almost all fonts should have a liga feature for fi, and all modern text layout engines should respect it).
