That is obnoxious as hell.

I kind of like having the page state in the URL like that - makes sending someone a link easier. See also: Discourse.

They should fix it by not pushing those minor state changes to history, though. Probably an easy fix.

I wish we could stop calling things "broken" just because they work in a way that's well thought out but unconventional. How are we ever going to make progress on UI design if everyone immediately gets chastised for deviating from more orthodox web behavior by even the slightest amount?

EDIT: lbarrow is correct that the hash tag navigation is borked. I thought people were just complaining about navigation to a previous site on the same tab. I stand corrected, I fully agree it's broken.