The thing is, with concepts like collective imaginary, the meaning is broad and fluid. Your question I think-as, to be frank, it is not worded that clearly-asks whether it is appropriate to compare democracy and Islam, one versus the other, as equal, comparable entities. Always plural for me if you are thinking of the collective noun (meaning young people): the youth of today are our future. My usage is like Ewie's. Maybe there's an AmE difference. A collective noun must describe a collection - that's why it's called a collective noun - a team of footballers, a parliament of elected representatives, a flock of birds. I think the key is to realize that 'couple' can be either a plural or collective noun and has slightly different meaning for each. As a collective noun , you refer to a group as a whole and imply that there is some sort of relationship between them. In AE this is what I hear most often. "The couple has just been told that their flight was canceled"
