I've been noticing it more frequently as well. It has changed the way I use HN. Now, I quickly scan the first page and open interesting stories in tabs. Then I quickly click More and do the same. Wash, rinse, repeat two or three times depending on how busy I am.
Another related issue: the expired page is remarkably stark and unfinished in comparison with the rest of the site. A minor nit, but since it shows up so often, it doesn't look great to the uninitiated.
I've often resorted to doing the same thing, but one problem with that is having to go back to the HN site to find the story to vote on it or comment. If a large number of people are pushing stories out to new tabs and ultimately ignoring the HN site after that, might it begin to affect the voting / ranking ?
Another related issue: the expired page is remarkably stark and unfinished in comparison with the rest of the site. A minor nit, but since it shows up so often, it doesn't look great to the uninitiated.