You don't need to post about them to report them.
It's better to tell an owner in private. As a mod, you can take action against the troll alt and tell an owner afterwards.
I feel like the alt rule should have a "To an extent."
People should be allowed to talk about alts by reporting on them once or twice and then leaving it at that for the day. It's freedom of the press in a way, so people can be informed of an alt and that it is an alt or a controversial user. That's just me, though. What do you guys think?