It's odd that my two replies above were both downvoted, even though I was just trying to be helpful to the OP. If this is the kind of response you can expect on the new HN for trying to help, it's no wonder this community continues to decline in quality.
How far can it go?
far.
Really far!
I'm not sure there's actually a limit.
I just think it gets annoying enough that people usually stop.
But sometimes, I have seen threads that get squished way up on the right side of the page!