Thanks, Jet_A_Knight. "Monitor" in this context usually means the same thing as "listen out" or "guard" (the word used in ICAO annex 12 vol II).
I am pleased to learn that you monitor 121.5 and I agree that it is most inappropriate to chat on 121.5
I also happen to think it inappropriate to chat on any aeronautical radio frequency.
And thanks for your answer, The_Messiah. I am very glad that ICAO, the RAAF, and the airlines do not share your view. Personally I am most reassured to know that if something goes wrong almost anywhere there will be a good citizen monitoring 121.5