What is wrong to do is use actual HTML <table>/<tr>/<td> tags for layout, because those impart semantic meaning about the structure of the content and should only be used for tabular data.
caniuse.com suggests only IE8+ supported it.
I'm not really a web designer so this isn't really my debate. I'm just pointing out that "HN does it" isn't really a strong argument. Something might be the best available option for some particular task but still not optimal for a whole host of reasons. The point remains <table> tags do carry semantic information so it's useful when possible to restrict them to situations where that semantic information is correct.
There is no such thing as Bootstrap div hell, that is utter nonsense.
If you used Bootstrap 3 seriously you'd also know there were LESS/Sass mixins for grids. No need to use divs with classes if you have that arbitrary dislike for genuinely useful presentational classes.