Some better standardisation of terminolgy would have prevented an exchange on the RT I heard about 18 months ago that went something like this:
Connie 123: "Departure, this is Connie 123 with you climbing five".
ATC: "Connie 123, climb to niner thousand feet".
Connie 123: "Climb twenty nine thousand feet Connie 123".
ATC: "Negative, climb to niner thousand feet".
Connie 123: "Roger, climbing to twenty nine thousand".
ATC: "I say again, climb to niner thousand feet".
Connie 123: "Ok, we're climbing to two niner thousand feet, Connie 123."
CX456: "Connie 123, this is CX456. She means climb to altitude nine thousand feet".
Connie 123" "Ah, now we've got it!. Climbing nine thousand feet".
The CX voice was a Brit who was crossing TD inbound at FL110 who obviously didn't want an RA! Admittedly, the Connie aircraft was pretty dull not realising that he shouldn't be cleared to an altitude above transition level, but the whole situation and the threat could have been negated by using standard terminology.