Like, the specific act of smiling with your mouth open = SUPER feminine/not masculine somehow?
It's the most arbitrary shit, I swear. lol
It was literally just made up out of thin air by chuds desperate to feel manly without actually having to do anything.
They soyface became a thing on youtube where you'll often have vloggers with their mouth open as the thumbnail. Apparently it made people more likely to click the video. It's not about femininity.
I remember before it was called soyface, I'd just feel upset seeing these wide open smiles. I went to a school with a lot of guys who have that look. They were often a frustrating kind of nerd who's world revolved around getting a job for a better gaming computer and sustained off of spicy nugs. When I saw all the "soyface" guys, it reminded me of them and how little I enjoyed being around them. Almost all of them went off to work in the weapons trade.
It may not have started that way but it quickly along with cuck husband meme came as a way to shit on any sort of feminine expression in men.