I would say the look and name of HN do impact growth in certain "demographics". That might even be the idea.

In that vein, discouraging memes, insider jokes, meanness, snark, and flamewars, also impact growth.

Of course, but it can also be engaging. It all depends on what kind of growth you want. For the size of the reader base, it's not very common to see people "on the team" comment something here on HN once the discussion turns opinionated.

It can be engaging when it is engaging. However, the median meme, etc. of the set of all internet discussions is not.