Buttoned standing or walking, Un-buttoned seated or relieving myself (obviously).
One exception for me..
If I have just run for a bus or train and over-heat, I'll take the jacket off entirely until I cool down.
Buttoned, otherwise you lose the look the jacket was tailored for.
+1
Wearing a tailored jacket unbuttoned when you are standing and walking about defeats the whole point of wearing a tailored jacket. You might as well be wearing a bloody windbreaker!
Generally I want to wear mine unbuttoned suits because I think it will show my personalty.If you have good personalty then must be go for unbuttoned suits.