What behavior by diners at buffets bothers you?

Anything other than coughing on the food, sneezing on the food, or not leaving any food left is really survivable.

https://m.youtube.com/watch?v=08F0Mw4lIdw

I am always amused when I see Japanese with meat and gravy, sashimi and cake piled up on the same plate. It doesn't actually bother me. I just find it amusing.

I'm fortunate in that I've not seen any truly horrendous behaviour in Japan, but one thing that bugged me was when a young lady took all of the seafood out of the seafood salad bowl and left only the vegetables. I thought that was very inconsiderate.

Oh, another time at a crab restaurant an elderly lady pulled out a plastic bag and shoved some crab legs into it. I couldn't stop laughing!

Loitering in front of the steam trays and blocking access. Unsupervised kids fiddling about with tongs or the drink machines. Getting the last of that item I really, really wanted!

I recently went to a lunch buffet at a nice hotel here. The room was busy, but there was only me and one other guy at the buffet. There was plenty of food, and no line, but this guy kept reaching in front of me to grab stuff. I finally got tired of it and said "Wow, you must really be hungry! (in English)" in a firm, loud voice. Then he bowed a couple times and backed off.

FIlthy dirty fingernails on little kids playing at the food counters and swinging their dirty hair into the food also.

This is why I stopped going to kaiten-zushi. Noisy kids standing on the seats. Kids pulling plates off the rotation belt only to quicky place it back. Kids caughing / sneezing so close to the plates. . . . .the staff @ these places certainly won't interfere in these situations.

And worse, their heedless moms doing absolutely NOTHING about the behavior.

In a buffet line when a person doesn't keep his distance and is standing behind you. In other words standing too close, breathing down your neck send's the wrong message and does nothing for your professional image. Save your dignity and stand back. Another one is don't use your fingers to grab food unless the table is intentionally set up to grab and go. Last of all don't nibble on the food from the buffet table as you make your way through the buffet line.

Once, in the States, my (then) wife and I went to an "all you can eat" buffet which included crab legs. Problem was, every time we tried (several times), there were never any crab legs. I don't know if it was because that place was busy, or because somebody was stockpiling. When it came time to pay, I explained why and only paid half. They threatened to call the police. I said go ahead and walked out. That was the end of that.

Japanese restaurants often don't provide enough space and access around the tables. For example, a v-shaped configuration shoved up against the corner of a wall.

Anyway, I stopped going to buffets a while ago, except for hotel breakfasts and salad bars. Mediocre food.

Entire Japanese families, sitting next to us and slurping spaghetti.. Yeah, this never fails to make me wanna throw up

Oh tell me about it ebisen! Thats so rude & barbaric. . . I like udon & ramen shops. But I dnt slurp n' sweat like a pig.

Well, I don't mind slurping of ramen (and other hot soups based Asian noodles), but tomato-sauce pasta slurping? I can't help imagining how the sauce sticks the eater's face afterwards...

Entire Japanese families, sitting next to us and slurping spaghetti.

Oh yeah, that one. I love the way they try and explain it by saying "it's hot, we have to slurp it down like that to avoid burning our mouths" and then do exactly the same thing with chilled somen noodles! Or any other kind of food for that matter.

On the other hand, I really dislike the way westerners lick their fingers after handling food. I bet that looks pretty nasty to Japanese diners, too.

I'll give Japanese some credit. In Hong Kong, I was eating out and other diners were discarding their chicken bones onto the floor.

Using fingers instead of tongs or the other supplied cutlery to fill one's plate/bowl/dish. Dirty habit.