Jon has a lot of opinions about how this is stupid or he'd never hire anybody who does that and so on, and yet Jon does these things anyway, because he's human and humans are fallible.
This is less obnoxious than it might be because at least Jon is self-aware enough to identify that e.g., this code written by "an idiot" was in fact written by J. Blow himself which suggests maybe he's an idiot. But his resistance to adjusting Jai in light of these observations is a (modest but non-trivial) problem with the language.
The necessity of sharp tools doesn't excuse needlessly dangerous edges.
Jai: “Yes, don’t do that terrible thing.”
Refreshing philosophy. Sharp tools have their place, even if they are dangerous.