Somehow Classy's page template ended up with two highlighted regions. It might have been around this issuebut I don't see a direct cause there. I think maybe the messages region was renamed highlighted, but there was already a highlighted region? No idea why the System template didn't have it then.
One a scale of 1 to WTF ... well, it aint closer to 1.
We should also check the other page templates to make sure we didn't make a similar mistake.
In the initial patch I removed the second one, which keeps highlighted in the same place as in the System template.