I somewhat get the argument, but if you're writing code in the HN textarea you're doing something wrong (for code where tab/space matters anyways). Like, any code editor will use the tab key properly.
Though, it sills maddens me there's no somewhat universal tab-entry in OSes like we have with enter (somewhat because there's a mix of shift+enter, alt+enter and cmd+enter). All of shift/alt/ctrl tab are usually also hijacked.