I am a young-ish man who has attended weekly Mass all my life. At the last Mass I attended in Istanbul, an elderly lady approached me while I was sitting in the pews and said that it was a sin to cross my legs. Is there any grain of truth in what she said, or is she merely an over-zealous, misled, scrupulous fanatic?
If you were in Istanbul, it is very possible that you were attending an Eastern divine liturgy. If that is the case, then it is true that some Eastern Christians consider it taboo to cross one’s legs, and some believe that the posture is too casual for worship (source). Perhaps it will comfort you to know that chastising strangers in a church is even more rude, but we might give some leeway to an elderly lady who may consider it her duty to instruct someone she believes to be a “disrespectful youngster.”
Respect to the elderly dictates that you not allow your embarrassment at being chastised motivate you to be rude to her in turn. (Rudeness to the elderly cancels out rudeness by the elderly.) In this case, you might have uncrossed your legs, stood and given her a nod of the head, and said to her, “I thank you for the instruction, madam. I am a visitor to your church and to your country and I am embarrassed to have inadvertently given offense to you.” Said in a completely formal and unsmiling manner, it is an impeccable means of indicating to her that she had completely misjudged you and should be embarrassed herself.