The text editor widget on their page is a bunch of "line" divs with individual terms being inside spans. If you add an inline style of
font-feature-settings: "calt" off;
or, more completely, font-feature-settings: "calt" off,"dlig" var(--ligatures,1),"ss01" var(--ligatures,1),"ss02" var(--ligatures,1),"ss03" var(--ligatures,1),"ss04" var(--ligatures,1),"ss05" var(--ligatures,1),"ss06" var(--ligatures,1),"ss07" var(--ligatures,1),"ss08" var(--ligatures,1);
to a single line div or a single term span, it won't do the healing. If one of the CSS pseudo selectors worked for these kinds of elements (I see there are a lot that apply to forms, but.. maybe :active / :active-within would work for editable spans?), you could have healing automatically apply to terms when they 'blur' / when they're no longer active.