I would write a formula that concatenates the comment text into a shared variable. This formula goes on the detail line. Write a formula to display the shared variable in the group footer and a formula to reset the shared variable in the group header.
Oh yeah, there would be a group created for Item, if that is the unique value. Oh and suppress the details as they don't have the message that you want.
I know that this is a rough outline. the shared variable declaration for all of the formulae would be: Shared StringVar Comment. Assignment would be using the := operator. End lines with a semicolon.
Yeah, this might be stuff you already know...just including for completeness.
Hope this helps.