When you truly love someone, things they might see as "flaws" in their own appearance can be charming to you, but constantly hoping you'll wake up one day and they'll have a difference face or body is a massive red flag. Part of being in love is loving every part of that person and accepting them for all that they are, and teasing them or making them feel insecure about something they cannot control is pretty gross, immature behavior. Caring about your looks and putting extra effort into makeup or clothing is one thing, but forcing your partner to alter how they dress or how they make certain facial expressions is a sign you probably shouldn't be together.
So, when a confused boyfriend decided to consult the internet's moral compass of Reddit's "Am I the as*hole?" to discuss an issue with his soon-to-be fiancée's smile, people were eager to offer their words of wisdom.