Cannot subscribe to atom feed

Checks out on the w3.org validator https://validator.w3.org/feed/check.cgi?url=https%3A%2F%2Fjoy.recurse.com%2Ffeed.atom but wont subscribe in newsblur.

They’re doing something special and giving NewsBlur HTML instead of RSS. I tweeted at them with an easily reproducible test case. Will update when they get back to me.