The layers and complexity of this film are its strong point. SPOILERS!

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Many of these things are open to interpretation. What is being thrown at the Catherine Deneuve character and what the people are doing under the table are not as clearly spelled out as the above poster states. Someone else may very well think it is something else that is going on under the table or that something else is being thrown at the Catherine Deneuve character.
But even beyond that if one does interpret those elements in the same way there is still a lot more that is open to interpretation and ultimately has depth.

For a film to be heavy-handed, it has to shove down the content, so that what you know is being thrust to you repeatedly. Belle de Jour however does none of this. Although, individual scenes may seem clear in the first viewing, a retrospective look would reveal that they may not be what one initially thought they were. The deeper one looks, the more mysterious this film turns out to be. His criticism of the bourgeois, church, absence of sexual freedom for women etc., are not the main ideas of this film although they've been touched upon as in like most of his works. So, if you think these thoughts have been shoved to the audience, think again. This can be seen as a surreal experience, even a mystery towards the end, but it works as a psychological drama and the film primarily explores the mind of Severine. The character arc is brilliant! Bunuel gives so little about her childhood, that it becomes open to interpretation. He also gives so little about her motives for her actions, but just enough to form ideas. I personally don't believe she was affected by trauma any more than her guilt over her fantasies/dark secrets. This is just one example of why it is not heavy-handed at all. Of course, the film makes it clear about what scenes were real and what were fantasies unlike some strongly surreal films, however that is not the point of this film.