It depends if we are talking of the way the act is executed, or its nature. If posters were only talking about the execution (posture, the dress, the tralala), then yes it is gendered. Women curtsy, men bow. But when some posters speak about submissiveness, this is about the nature of the act (or at least their way to describe subjection). In reality, the nature of the act, subjection, applies equally to men and women. Saying that an act of "submissiveness" feels like a feminine thing because it is a submissive act, is a sexist stance. It contributes to propagate demeaning stereotypes about women. It may not be the intention, but it is the consequence. I always have a thought for women reading this kind of lines.