This is something of a major problem to solve with one of two major outcomes that aren't mutually exclusive: 1. The blocking comes up with many false positives

This is something of a major problem to solve with one of two major outcomes that aren't mutually exclusive: 1. The blocking comes up with many false positives blocking many things that shouldn't be blocked (the John Graham-Cumming issue) 2. They don't catch everything, which is very likely, and the work required to get around blocking by teenagers is minimal.