I've violated that rule pretty much every time I've been on the tube and I never had anything but positive responses (and my head is still firmly attached).
I long ago made a decision that saves me enormous amounts of headache: if you say or do something I will interpret that in the simplest and most straightforward way possible without trying to second-guess ulterior motives or secondary (or further) layers.
Exceptions: poetry, music, jokes and other cultural expressions.
Before then I was always chasing my own tail with 'what do they mean?', which is pointless, if they meant something they could say that particular thing outright and get it over with.
This is symmetrical, so, I don't want to 'wash my hands', I would like to use the toilet. When I'm hungry I say so and when I say 'no problem' it really means that so we can move on.
All in all this made life a lot easier, though from time to time it can make for comedy.