It's the quality of the debate, not the value of the position
Note that only applies to subjective topics. If you're commenting about a purely technical topic then the voting system does seem to work more effectively.
Nor does having downvotes cause any automatic placement adjustment.
I review their comments manually to tell me about the person. It's a qualitative evaluation, not purely quantitative.
> I use applicants HN score, and comments as hiring factors.
I get reviewing the comments manually, but what could you use the score for besides a group think filter? Might be great for a sales position ...