I’ve never in my life been told that elbows on the table, or cutting up all of my food at once, are poor manners. I’m disgustingly guilty of both of those. I can’t imagine cutting up each individual piece of food right before inserting it into my mouth
I don’t say “bless you” or any alternative of it when people sneeze, I don’t use napkins, I don’t give girls special treatment (though being a nerd with nerd friends, girls are a bit uncommon in our realm), I have a tendency to reach across the table for things (I hate interrupting conversation to say “Please pass the gravy” if it’s within my reach. It feels ridiculous), I’ve also been told recently that the way I cut my food (how I hold the utensils) is weird.
I’m sure there are a good dozen more things that’re expected of me that I don’t do, but whatever I do is instinctive and I really can’t think of it at the moment.