Men in tracksuit trousers (always grey!) with no pants. Yes we can tell. No we don't want to see it. Yuk. It gives me the impression they're a bit thick, a bit rough, and likely to drink too much and get in a scrap.
I heard myself telling DP to 'open the curtains properly please, the place looks like a bloody squat!' this week. When he'd opened one half and left the other. I've turned into my DGM. Not that she would have sworn, that's common...
People who are either in stained, grubby clothes (usually a tracksuit) or their kids are snotty and dribbly and grubby and they make no attempt to wipe their faces. Poor little things, it hurts to have a permanently snotty nose and lip when it gets chapped.
People who post stuff for sale and the carpet / room in the photo is piled high with clutter and filthy. Usually saying 'needs a clean'. Well clean it then you minger, no one wants your dirt!
I'm sure there's more, but most boil down to my DGM and her worry about being perceived as 'common' and the lengths she went to, to show she wasn't. She was very poor growing up, had to be taught how to wash as a young teen and never finished school. She was mercilessly judged, and spent her whole life trying not to be 'common'.
I remember the first time we got chips for lunch from the takeaway in town, and she was worried where we would eat them. As kids we suggested the bench on the green - you'd think we were snorting coke from the way she tried to conceal what we were all doing, while surrounded by other families eating chips!