passing comment vs remark

passing comment and remark both are nouns.

Word	Noun	Adjective	Verb	Adverb
passing comment	Yes	No	No	No
remark	Yes	No	Yes	No

As nouns, remark is a hypernym of passing comment; that is, remark is a word with a broader meaning than passing comment:

passing comment: an incidental remark
remark: a statement that expresses a personal opinion or belief or adds information

Other hypernyms of passing comment include comment, input.

passing comment (noun)	remark (noun)
an incidental remark	explicit notice
	a statement that expresses a personal opinion or belief or adds information

passing comment (verb)	remark (verb)
	make mention of
	make or write a comment on