Someone’s headcanon doesn’t take away from anything; this is a case of addition, not subtraction. Literally basic math.

desbian:

Y’see, normally headcanons are fine. It’s when a character is canonically a part of a minority, and someone has a “headcanon” to take them out of that minority group, that there is a problem. It takes away representation, which NB folks especially don’t get a lot of in media. And especially in this case, someone calling Frisk or Chara a boy or girl sends the message to everyone who sees it, “if someone goes by they/them pronouns, it’s perfectly okay for you to disregard that and use he/him or she/her pronouns for them instead”.