It's half dead bacteria, it's not supposed to smell like a bed of roses.

Travel messes with a lot of people's systems.

That’s not remotely true. There are plenty of health conditions that affect this. Alcohol consumption can affect it. Completely normal diets with specific foods can affect how stinky your poop is. Non standard but healthy diets also can do the same. There’s a lot more to it.

I can safely say there’s no person whose shit I want to be smelling, regardless of their diet.

I feel like you're not picking up on the central point of "worse is worse than bad".

>A door stops airflow? No.

I mean, it literally does. Put something that smokes in a bathroom, open the window, close the door, and caulk the gaps. See how much smoke phases through the door.