Very nice essay, but he probably should have left this part out.
Abstinence from meat is required under penalty of sin on Fridays during Lent. Abstinence and canonical fast is required under penalty of sin on Ash Wednesday and Good Friday. Fridays outside Lent which aren't solemnities are penitential days which are to be observed by some sort of self-denial, and arguably that is also under penalty of sin.
Yeah I noticed that and thought to myself 'I dunno if I'd quite say that...'.