No.

The discussion should meander in any direction the votes and scoring allow it to.

If the voting supports it, it is on topic ipso facto.

Not at all, that's why we have moderators. Hacker news is interesting because they stay focused on the right topics. If you let people just talk about whatever they want, you're just gonna get an inferior Reddit. Topic != "Whatever we want to talk about", the topic is very often the technical and technological aspects of a story or article. Talking about politics on HN is definitely "off topic".

Email mods at hn@ycombinator.com if you see a pervasive violation of HN's comment guidelines.

Flagging and voting also help, but for wildly out-of-control threads, direct contact is more reliable.