I couldn't reproduce - you can just close the modal that pops up with no adverse effects.
In any case, when an article is paywalled, you generally get around it by clicking the "web" link under the HN title, then clicking on the top result in Google.
"You have reached your article limit." Disappointing.
Incognito mode or using another browser is usually enough to work around these. (I haven't read enough economist articles this month to check for sure on this site.)
Delete all cookies for the site, reload.
Works in this case, won't on most modern paywalls. New Yorker for example uses Supercookies/Fingerprinting to give your UUID back to you.
In general, click the "web" link at top of page to google search, then click through.