Slightly OT, but I remember once when boarding an MH flight where a backpacker in his late teens / early 20s plonked himself into a J seat and immediately removed his shoes. The smell that wafted through the cabin was... revolting.
As the rest of us politely tried to hold our breaths and endure the journey, a rather matter-of-fact looking Malaysian (or Singaporean, can't quite tell) "uncle" got up from behind the backpacker, pointed him to the overhead storage, and said, "Keep your shoes up. Very smelly!!" And the backpacker obeyed, ever so ashamedly.
The rest of us couldn't thank the "uncle" enough.