Kiss kiss is used by sweet people online as an indirect form of expressing affection without too many explicit gestures. Girls interested in you might use this expression instead as it doesn’t reveal too much and risk being overt about their feelings.
Though XX can be written either uppercase or lowercase without altering its meaning significantly, capitalizing it may add emphasis and express greater affection. However, it can also be used as a casual ending or to show closeness.
One “X” after someone’s name signifies they are your friend; two indicate best friends or potential romantic partners; three Xs show they like you quite a lot; four indicate an intense attraction towards you.
Importantly, XX has only recently become an emotional signoff. Before, this phrase was only ever used in more formal or intimate settings – for instance when showing gratitude or respect towards an elder or superior. Nowadays it is frequently used as an emotional expression online – such as when thanking an individual. For instance, Dana Schwartz from Hours Agency in New York often signs her emails with multiple XX’s to add an intimate feel and make each message more personable.