Another thing that's not really a saying but a reflexive habit: People accepting a compliment that's not really directed at them.
"You have a lovely wife."
Oh, did you design her yourself?
But, "You have a lovely wife." (and that sort of comment) is actually an insult!
The one saying it to you is expressing their disbelief in the fact that such a "lovely" woman would ever have anything to do with you...
The "Thank you"-response only shows that you also find it quite unbelievable that such a person would have anything to do with you -AND implies that you have (had?) some kind of special mojo that got her attention at the time...