I used to work with a guy about 23 years ago. His name was Stanley. Funny how I remember his name now.
He had a bit of an issue. He used to grunt, like really loud grunts that reverberated through the office. Constantly. I thought it was funny, it was a gross noise but it didn't "trigger" me like some noises do. But it triggered a few other people. I just found it amazing someone would come to work and sit in their cubicle and grunt like a hog all day. Every day. Initially I didn't know his name, only knew him from the grunting so I started referring to him as "grunter" and the name stuck.
A girl at work had to work with him and she couldn't remember his name, kept almost calling him "grunter" as that had become the poor guy's nickname (never used in his presence) and that was all she knew him as. People asked him why he did it and he said that he always felt like he had something stuck in the back of his throat. Eventually he did stop doing it.
Around the same time I signed up for a Thai cooking course with a friend. It was great, once a week for 2 or 3 months, and we learned how to make some really awesome food. There was a lady attending the course, she was an immigrant who was maybe early middle age. She didn't have to pay for the course or contribute for ingredients, I am not sure if it was a requirement for using the community centre or if someone was paying for her. She was apparently there because a counselor thought she needed some social contact, she felt really disconnected in Australia. You can probably guess how this is going to turn out. Well it became pretty obvious why she had trouble making friends. She would pick her nose when she thought nobody was watching. She would sniffle and wipe her nose with the palm of her hand while she was preparing food. She would cough vigorously as a result of the sniffling and not cover her mouth nor even turn away while she was helping prepare food, just constantly cough and splutter over the food. For the first 2 or 3 weeks the teacher would assign us into groups, and nobody would eat whatever food her group prepared. Seriously. As the course went on the teacher let us form our own groups and each group would block her from working with them. A wall of bodies would magically form if she tried to go near any food. One time I was preparing the broth component of a soup, and I had some stringy stuff that I had to tie into knots and then drop in the soup (it would disintegrate if not tied) while another group prepared some meatballs to go into the soup and other groups prepared other stuff for the meal. The other groups would move around if they saw her come near them and block her from going near their food, and she spotted me working by myself and came over to help me. I felt awful about it but if I let her touch the food I was working on then that was 2 or 3 teams' effort wasted, so I kept my fat arse between her and the food. Considering that she was clearly in a fragile mental state to begin with, I can't imagine the damage done by the way she was treated week after week. But there seems to be this unspoken social rule that no matter how gross someone is, you can't mention it. The soup was awesome, by the way. No unexpected flavours.
I have a friend I have mentioned before. He snorts and wipes his nose with his hand, then wipes his hand on his trousers (leaving a visible snail trail on his trousers if they are dark). He also never washes his hands when he goes to the toilet, not once in the 43 years I have known him. But he really hates that I consider him so gross that I won't shake his hand unless I can cover my hand with something. So he tries to stick his fingers in my mouth. Literally. He knows I could break him in half but he also knows I detest violence so he is safe (ish). That's the thing, people don't like being made to feel as if they are gross. If people make "trigger" noises around me I will look at them, kind of cringe, shudder, furrow my brow, maybe look a bit grossed out, and if they notice that then they either try to cut down on the grossness, don't care, or they go out of their way to make me pay for daring to have that reaction. Now the number of people who would do the latter is 2 or 3 out of many jobs and maybe a thousand or more people that I have shared office space with over the course of 36 years, so it's not an everyday thing, and not something that I would expect a person without such triggers to notice.
Yes, of course the idea that some (notice I said some, not all) people with gross habits could stop if they wanted to, but they are either not aware or they just don't care, is presumptuous. Because I don't know what is going on in their heads. Not quite the same thing, but I have a friend who crunches his food so loudly you can literally hear him from the street when he is on the sofa watching TV, eating corn chips. With my dodgy hearing. Through his double brick walls. He also shoves huge amounts of food into his mouth and tries to carry on a conversation at the same time. One time years ago he phoned me and I could barely understand him, it sounded like he had a tennis ball in his mouth, and I asked him "are you eating?". He said "yeah, I just got home with a burger and thought I'd call you so I'd have something to do while I eat it". I asked him if people at work complain and he said they do. I pointed out that if people complain then it's really bad, we have people at work who eat loudly and nobody says anything. I asked him if the people at the office across the street complain as well. And yet he eats as quietly as a church mouse if he is with his girlfriend. Otherwise he just doesn't give a toss.
A lot of it is cultural as well, so if you work a lot with people from certain cultural backgrounds you will notice this stuff more. I worked in one country where there was a bathroom for our office with one wash basin to wash your hands in, but I never saw anyone wash their hands. Ever. Ones and Twos. Never. At first I thought that was kinda gross, but then I realized that the actual purpose of the wash basin was for ejecting stuff from one's sinuses into. I would like make a bundle of paper so that I could touch the taps (yes, there was stuff stuck to the taps) and wash my hands but I just gave up on that and took to washing my hands once a day at home (just for the 3 months I was on that project).
If you are triggered by certain noises then you will notice stuff. Like how someone will sit in a corner and make occasional gross noises, but the frequency and volume will go right up if there are other people around. Or if they are sitting in a meeting.
I've got lots more stories about gross people. Stuff that triggers me I never forget. But that's enough for one day.