it comes from trans subreddits like r/traa and r/egg_irl, where posts of the "the person reading this is a good girl UwU" variety had CWs because they could cause dysphoria to non-transfems (there was an equivalent "post assumes reader is transmasc" too)

here? tbh, most of the posts with that CW don’t even assume anything about the gender of the reader, it’s just posts about transfems. and i agree with you i don’t super like that "this post is about transfeminine people" is seen as warranting a CW.