Brothers, especially elders who are married, sit on the aisle seats. If his wife should sit there instead of hm, it could look like she is unsurping his headship.
Sisters should always wear nylons. I think this rule is more relaxed now, but once upon a time, it was quite scandalous to wear a dress or skirt and have bare legs!
Sisters should always have their hemline well below the know, and “even more so” if having a part on stage.
A brother may have a well-kept moustache but never a beard. (I understand this rule may also be more flexible.)
A sister singing “so let’s watch how we talk and watch how we walk” may be construed as a sister - gasp! - giving counsel, so some song lyrics are now being adjusted.
One shouldn’t buy stuff second-hand or from garage sales because you risk picking up something which could allow demons into your home.
Oh so many more....