the last time giles says jenny’s name in canon and indicates that he still misses her. and it’s not for him. it’s to help buffy
like he definitely 100% would not have brought this up unless it was relevant to buffy’s own struggles (which it is) and it could possibly help buffy understand her own emotions and feelings (which it could) and i am just. this says so much about why he never mentions her again. because giles only brings up his pain and his struggles if they can be used as examples to teach and guide and learn from his bad example. he never brings them up as attempts to find comfort.
he knows that kids half his age are not emotionally equipped to deal with his own problems. and the only person who could possibly listen to him and be his friend is the person whose name he no longer gets to say unless it’s in a context that could possibly help other people