The first one is indeed non-obvious, but the remaining snippets presented as bugs would not pass a review unless hidden inside 1k+ LOC PRs. Some are so blatantly obvious (seriously for loop and not passing current value as variable?) that I'm surprised that authors have listed them as if they're somehow special.
> for loop and not passing current value as variable
In most languages, current for loop value is always accessed a variable, not a reference. The only languages where it's not the case that I know of are Go and Python (JavaScript used to also have this problem with for(var ...), it was fixed with for(let ...)). So if you don't regularly write Go, it's easy to make this mistake.
