What should not be done to buttonholes on suits, according to customs?

Buttonholes on suits have a specific tradition concerning their use and maintenance. Keeping them uncut unless the owner specifically desires to do so aligns with customary practices in tailoring. Traditionally, the buttonholes on suits are often left uncut to maintain the suit's overall look and integrity until the owner is ready to use them. This practice preserves the neatness of the garment, as cut buttonholes signify that the suit is intended for active use, while uncut buttonholes maintain a crisp and polished appearance.

The other options do not adhere to the customs surrounding buttonholes on suits. For instance, sewing buttonholes closed after use would contradict their intended functionality, as buttonholes are meant to be used for fastening. Additionally, altering a buttonhole's size for comfort isn't a standard practice, given that buttonholes are designed to accommodate their respective buttons effectively. Lastly, the assertion that buttonholes must always be cut before wearing would undermine the tradition of preserving the suit's aesthetics until it's ready for informal or professional wear.