Wanted to point out that Airbnb is engaging in what's referred to as "black hat UX (user experience)" design. There is a near-permanent notification dot on the Messages tab of my hosting dashboard.
This has nothing to do with cookies and it's not a bug. I work at a SaaS company — I'm familiar with both front-end dev and UX/UI design.
Airbnb is intentionally employing unethical design tactics to increase user engagement, and it's fairly annoying.