Scott, couldn't agree more, we get it all the time especially with the US crews, they read back headings and FL's without any prefix, therefore 280 for example could be a FL or HDG??????
Sometimes, no callsign is used with these readbacks or for frequency changes as you said. It all results in unnecessary RT and phone calls, which does not help when you are busy. Sometimes they just disappear with no reply, wonderful.
It's not just the US crews, but they are definitely the worst offenders. Maybe one day mode S in a user friendly form might help? I'll probably be retired by then and I've still got a long time to go!
