So I take it you never read the sefer of which you refer here. I’m quite familiar with Rav Dovid Cohen Shlit”a, and he’s not “ois poisek” because you don’t know the source for this alleged mitzvah. But shtarb min nisht fun a kashye, especially when the Chazon Ish quoted earlier clearly states otherwise. Quoting a title of a book as a proof is not “oisgehalten”. Every halacha has a mekor. Even not walking over a child has a mekor (a Rashb”a not to be mezalzel in minhag nashim zekeinos- “old wives’ tales” and modern poskim who bring that one down as an example.) I have heard the “he doesn’t quote it because it’s pashut” svara when it comes to explaining why the mechaber didn’t quote anything about uncovered eggs, onions, and garlic being dangerous. I have never heard this applied to speaking Yiddish.
The one thing I will say is that a friend of mine got into a shtus of growing payos behind his ears in Eretz Yisroel. He was advised not to cut them off because even though there is no svara to grow them, cutting them off would make him feel like he’s poreik ol.