Cannot deeplink on indie hackers.com

I'm trying to share a link to one of my forum posts. (https://www.indiehackers.com/forum/show-ih-browse-every-book-hyperlink-posted-on-marginal-revolution--KljmTs1xVnGB1CuEeV-) If I click the link which using indiehackers.com, I can reach the post. But if I open an incognito browser with no sessions, or cut and paste the url into a new tab, I am redirected to the root url.

Is this a bug or a feature? I'm using latest firefox on debian stable.