This is a rare instance in which the downvotes themselves actually answer your question.

The downvotes demonstrate that the community has decided it's so obvious that these aren't threats that it's not even worth explaining. We on the Internet are viewing these comments through the prism of our own experience viewing other online comments, and that experience causes us to "just know" that they aren't threats. "just knowing" is an argument that wouldn't stand up in court, though. Nothing in law is obvious

Reasonable person standard is one of those situations where "just knowing" is actually an argument that stands up in court.