Classical Fencing Jackets' style used in athletic competitions and training(aka using buttons rather than zippers).

Hi. I'm relatively new to fencing and I can't seem to find if there are any FIE regulations prohibiting suit customisation like adding buttons to a jacket. I love all types of fencing and when in athletic competitions I only see people using modern zipper fencing jackets. I was wondering why did people stop using button-up (Victorian era like) jackets and if there are any rules prohibiting me from just adding buttons to my jacket since it is more practical for me to button things rather than using a zipper, as well as looking more unique. Can anyone help? Thanks.