If you write a love letter to a boy who has already gone to work, will it be stereotyped by jokes?

Of course not, provided that your face value is passable.

If you are really ugly, the person you secretly love will think it is a joke in itself. He may read the letter to the people around him, then tear it up like a joke, throw it into the trash can without hesitation, and clap his hands as if there was something dirty on it. Then you will be regarded as a joke after dinner by everyone.

Don't ask me how I know, because I have experienced it.