Several people on the internet commented on my former picture that they loved my smirk. I wasn't intentionally smirking, that's just how I am.
Yes, I find large smiles threatening, but then, so do most higher primates. An open-mouthed "smile" is often a symbol of aggression or fear.
One of my psychology texts had four smiles next to each other. Two were apparently "real," and two were "fake." It was meant to prove the ease of discernment between them. I failed. I chose the smaller smiles as real. There was something around the eyes that I completely missed.