There's the written rules, and then there's the enforced rules. Political posts might not always be against the rules-as-written, but they're almost always against the rules-as-enforced-by-flagging.

HN moderators will tell you flagging is a user voting phenomenon they have control over, but it's not - I was also told my flags don't count, because mods disabled my flags from counting because I flagged things different from what the mods wanted to be flagged. Flags are not a type of user voting, they are a centralized moderation thing.