Some political threads get flagged and others don't. There was a thread about austerity and Nazis a couple days ago.
If you're looking for a blanket rule ("all politics" or "no politics"), we don't have those.
Yes; that was happening before the experiment, too. Most general political news has been officially OT on HN long before the experiment, and remains so under the general guidelines. The experiment was effectively a ban on that small subset of political content that would otherwise be generally within the guidelines.