By whom?

Dang and co. You can read his comment history for explanations if you're curious, using https://hn.algolia.com/ to search.

It's not nefarious as is implied here, but it's not totally "organic".

The HN Algorithm, Dang, PG, and the HN users.

If you include software, mods, and community, that's the totality of the system, in which case I don't think you can call it manipulation; can the system manipulate itself? But it's not clear to me what the GP meant by that word.

I'm not sure what you mean by "manipulated"? unless you mean the general category of "curated", "moderated", "censored", etc., all of which seem to have the same factual component and vary mostly by the feeling they express.

I don't mind which word you use but I do want the community to understand what we do and that we're open about it, at least in the sense that when people ask questions, we answer them.