BTW I too was was taught to use a comma with quotation marks, but even where it seemed ridiculous. Not quite everywhere, so e.g. 'He said "No."' was thought to be all right, so it was conceded that that was sufficiently different from 'He said no.', but as Heathfield says above, if the quotation in that position formed part of a sentence it had to be e.g. 'He said, "No, it's not."' I don't really see that even Heathfield's Poirot example above is a convincing reason for nostalgia for that carry-on.
I dropped it aeons ago in favour of the practice of only putting commas where they are absolutely necessary, when I had learnt languages which insist on commas before relative clauses, whether defining or non-defining, thus losing the distinction in writing in spite of its presence in speech. And then disconcertingly learnt languages which don't have that distinction in either, and having the literally unedifying task of trying to teach it in those languages. Having learnt the importance of NOT putting a comma before defining relative clauses, I could only stomach the absurdity of putting in
purely decorative and actually misleading commas in those languages whose speakers would otherwise think me illiterate.
When I was in a position to hold out for what I believed actually promoted literacy in English at least, the only language in which I have full native-speaker competence, I went through theses with a machete, chopping my way thru the forest of commas (and gaily re-splitting infinitives). Doggedly chanting Heathfield's mantra about clarification of meaning.
So Heathfield, it seems there are at least three of an age on here. Teach William and Henry, did you? What's this apostrophe after their surname?