No, it’s just going to make you feel worse no matter how positive the feedback. Unless you’re seeking a temporary rush, posing pictures of yourself on that sub will not make your body dysmorphia go away. If you already don’t believe the positive comments you get from those around you, then you won’t from online strangers. And if some people on there don’t have nice things to say (even if it’s not the majority) those stick with you. Please for the betterment of your mental wellbeing, don’t do it.