海外で働く人いわく、日本人が知らずに海外で犯しているマナー違反で個人的に最も気になるのは「鼻をすすること」らしい - Togetter

This page discusses how Japanese people unconsciously commit etiquette violations abroad. The most notable issue highlighted is "sniffling" or snorting nasal mucus, which is offensive in Western cultures. While Japanese culture discourages blowing one's nose in public, Japanese people tend to sniff instead. However, foreigners find this behavior unpleasant, considering it "dirty" or "lacking self-control." This becomes problematic during video conferences, and many foreign colleagues endure it silently. The cultural gap is significant, requiring Japanese workers abroad to be especially mindful of this habit.