I think he would ask you to avoid this because it is overly polite, and might not be well received. The literal meaning is a very polite invitation, for the person to give their attention to the thing you have written. There is a possible implication, that you feel it necessary to remind them to be kind, and to give attention. As a recipient, i might wonder 'have i not given enough attention before now? does she think i will not give attention?' If you included it every time, it would be clear that you are not considering it an important part of the message. It would be considered a platitude / polite flourish. but then it would be a little impolite, as you should not make an unnecessary requests for action. Routine, or regular inclusions of expressions like this would usually be passive. You would wish the person well, or thank them for their time.

It is polite. A polite way of asking someone to do something.