>is it true that overusage of the ending particle よ can come off as arrogant/know-it-all-attitude? Yes, it is true. I think the main implication of ”よ“ is "Look!, Attention!", which turn to mean the derivatives including, "I know (and you don't know)" "you should know" "I found it !", "It is me who found it", "わたし、今度、結婚するんですよ” （Attention!, implying ""My marriage is worth your attention") "わたし、今度、海外旅行するんですよ” （Attention!, implying "I am great") "わたし、日本語を10年、勉強してるんですよ”（Attention!, implying "I am great") ”見てみて、すごいよ、富士山だよ！” (Attention!） ”おまえ、すごいよ”　（"I know/I found" you are great) "そんなの、当たり前だよ” （”I know (and you don't know") "ひどいよ、そんなことするなんて”（Attention! You should know!) "あら、その髪の方が可愛いわよ(You look prettier with that hairstyle -> "You should know -> I know and you don't know" Yes, too much use of "よ” could give an impression of "arrogant/know-it-all-attitude", in other words, simpler, ”ウザい”、”めんどくさい” >what other mistakes do you think foreigners tend to make regarding these kinds of particles? One of the common mistakes foreigners tend to make, I think, is that they often/sometimes use those particles including よ、ね、なんだ in DISCUSSION WRITING without fully understanding the emotion they indicate, and result in conveying inappropriate impression unfortunately. I think the best practical solution is NOT TO USE THEM. Most of the Japanese, including me, don't use those particles carelessly when writing, because we know their side effects. I'll show you examples later. (To be continued)