It's the "historical-ligatures" feature of used font, if you aren't in the reader mode already, F12 and

    document.body.insertAdjacentHTML('beforeend','<style>p { font-variant-ligatures: common-ligatures discretionary-ligatures contextual;}</style>')

should turn it off. (Was "too much" for me either.)

But besides this, I found typography of that article quite nice; interesting that there are thin spaces before "?" and "!" and wide spaces (not double spaces) after sentences - also "old school" (and often frowned upon). I guess some WP plugin does it, but I admit don't remember seeing seen this anywhere else recently. (And I like it.)