30-day money-back guarantee

goronskyVery technically speaking, can the comma be eliminated in these two phrases?

Technically, no: a 30-day guarantee, a money-back guarantee.

But the oral and written phrase (here in America) is 'a 30-day money-back guarantee' and 'a 60-day no-risk trial'. I often see them with a comma, and to me it's wrong. You agree?

'Thirty-day' and 'money-back' modify 'guarantee'; hence, no comma betwixt the two.

PS That writer's manual for theses and term papers is awesome.

goronskyYou agree?

Not at all. While the comma is formally correct, advertising takes shortcuts which are now widespread and ipso facto acceptable.

But they're not coordinate adjectives. I would think they're cumulative adjectives.

In 'a blue wool sweater', we do not need a comma between the words 'blue' and 'wool' because the two adjectives are not coordinate adjectives; they're cumulative adjectives. It would sound illogical to say 'blue and wool sweater' or 'wool blue sweater'. The same could be said for 'a 30-day and

goronsky 'wool blue sweater'.

That is merely an error of traditional word order.

goronskyThe same could be said for 'a 30-day and money-back guarantee', and, similarly, 'a 60-day and no-risk trial'.

I don't think the same can be said. Both of those phrases seem quite reasonable (if not native) alternatives.

The short answer, then, is 'yes'; keep the commas in those two phrases, correct? Can't find a definitive answer (across the pond) over here.

30-day, money-back guarantee
60-day, no-risk trial

goronskyCan't find a definitive answer

I don't think there is one. Dealer's choice.

Which hand would you pick?

It depends—formal tender? matchbook cover? It's not worth worrying over until I really have to do it.