An why not? I sometimes sign my letters 'with kisses on the bottom' and there are the little x's in a row. I let the recipent decide my intent.
If I can bring a smile to someone's face or a glow to their cheeks then I will. A little mild flirtation is good for the soul. It lifts the spirits and lightens the step and done discretely and kindly it harms no one.
xx
John