I agree almost any response means "yes", but "r" or "c" is more of an answer (technically, "r" = "received" not "yes", same with "roger" in voice.)
here's a similar question:
decades ago someone told me didit dit (.. . or "i e") can be used to mean "is the freq in use" or "QRL?") who else uses that? I think I heard it used back in the 70's but not since then. I use it all the time, since its much faster and less interfering than all the symbols needed to send "QRL?" (7 vs 54 dit-lengths).
so, didit dit as the question and dit as the answer is about as short and low impact as you could get!
AA4Q