People can feel so strongly about someone's "bad manners" or "discourtesy" that they cut them dead, even if they were close friends. They find the other person's conduct so repulsive and embarrassing they just don't want to be exposed to it again.
I remember carefully avoiding one woman after she invited me for a birthday drink and then steadfastly ignored me while chatting busily to her other friends. Jenny and I gave another friend the brush-off after she turned up an hour late for a (by then overcooked and inedible) meal. She breezed in without any apology as if this was perfectly acceptable.
Table manners can be a big bone of contention. I don't even notice if someone always talks with their mouth full, while someone else will be cringing with distaste. I loathe messy eaters who spray crumbs and food fragments in all directions, while other people aren't remotely bothered.
Conversational habits are another bugbear. Is the person who gushes non-stop about themself tediously narcissistic or admirably self-confident? Is the person who hardly says a word a good listener or a lazy deadweight? Is the person who finds the hole in every argument a pain in the arse or a breath of fresh air?
Attitudes to personal criticism vary widely. I can take very heated criticism without turning a hair, while others are grievously offended by the mildest challenge. I know I have plenty of faults and I don't mind if others point them out - as long as they're polite about it. But my father took the slightest criticism as almost a declaration of war, and would sulk for days.
What's meant by good or bad manners is a tangled question. But one we shouldn't waste too much energy on. If we're so obsessed with someone's eating habits that we pay no attention to what they're saying, that's absurd. It's jolly bad manners in fact.
