Oh I don't wonder :) After a few years experience with analysis you sometimes see certain patterns in papers which strongly suggest bugs you've experienced, phenomenon in the data set you're already familiar with, and hacking/overfitting. And some of the languages are specifically designed to keep running and produce wrong results rather than crash and abort: a cynical man might say this is a feature not a bug and that's why they're popular.

As a non-wealthy, non-academic, this isn't a battle I'm interested in fighting directly. There are other hills I'd rather die on :)

In my experience, not reliably. And when following up something suspicious, you'll hear "I don't know, I didn't write that".

That's only more the reason why they have to publish it.