I agree these are factors that can possibly make digestion worse, but for the majority of healthy people, it isn't going to cause them I'll affects. I've ate a pack of sugar free gum a day, ate multiple quest bars, and I suffered no real world consequences. No running to the bathroom, constipation. Not saying some people aren't sensitive to these things, but I feel like for the most part our digestive system is more resilient than we give it credit for and we don't need to constantly limit ourselves and the food, gum, coffee in a quest to repair or not damage, or optimize digestion.
I personally feel the reason we see so many people on aas forums complain about digestion is from consuming such high volumes of food day after day to move the scale up. It's not because they ate some junk, or put sugar alcohol packets in their coffee, or didn't go organic.
Yes the food volume is needed to grow to unnatural levels, but it is a double edge sword, as we have more digestive issued than the general population who eat 2-3 k calories per day and more processed food
I guess in summary we just disagree to how sensitive the human digestive system is to more processed food and our personal experience influences the way we think. You said you have some ibs issues, where I can tolerate any food, but I have had discomfort trying to force down 6+k calories of clean food on my high or refeed days. I was able to eliminate the discomfort by throwing in a little not so clean food with my clean meals and cut down on the bloated feeling and woke up leaner. When I say leaner I don't mean less bodyfat, just not distended with a stomach full from yesterday's meat and fiber, lol.