I'm interested in what you think distinguishes it from marketing and better UX.

From what I can tell, it seems to be a term predominantly used by startups who want someone both technical and interested in the marketing side of things, likely since they don't have the budget to hire more than one person.

I think HN seems to have a negative view of the term, most likely because it seems like such an empty buzzword. And the use of "hacker" seems to play to a childish mentality of software engineering. (EDIT: I'm thinking in terms of use like "rockstar ninja hackers" job postings)