Some of these sound just as made-up as a lot of Western dining "rules." Maybe someone more familiar with the culture can say whether or not these are true faux pas in an everyday ramen shop or similar.
In all my decades of using chopsticks, I've never had a splinter poke me. But I've seen people rub their chopsticks then complain about splinters.
But the internet informs me that the composite chopsticks that I am used to seeing went away during covid and now disposable wooden chopsticks are the norm.
I almost associate the cheapo reusable plastic chopsticks with some food courts or Matsuya at this point.