Even worse, both the popup, and the dismissal of it, enter the back stack. So to get back to HN I had to click 'back' twice [edit: thrice of course].
I think it's an honest mistake. The fact that you dismissed the popup seems to be stored in a cookie, so it bothers you only once ever (twice if you use the back button).
Sidenote: since I'm in the EU I think you need to need to ask me for permission, but let's not open that can of worms.
I mean I don't doubt it's an honest mistake, but it's also an honest mistake that wouldn't have had the opportunity to be made absent the decision to annoy the user with the signup modal anti-pattern.
It's now bothered me twice, 2nd time on a dynamic search page (and, BTW, after I subscribed by hitting the top level link to "Newsletter" :-).
Indeed, get rid of it, your site design is so sparse it's hard (I think) to miss the "Newsletter" item at the top. Or put it inline somewhere else, e.g. at the bottom of the list, if someone's bothered to scroll down that far the odds they're interested in the newsletter are quite a bit higher, I'd think.
I think it's an honest mistake. The fact that you dismissed the popup seems to be stored in a cookie, so it bothers you only once ever (twice if you use the back button).
Sidenote: since I'm in the EU I think you need to need to ask me for permission, but let's not open that can of worms.