It actually also errors out from the "Strict" preset in Privacy preferences in Firefox. Clicking "Customize settings" on the StackOverflow popup thing results in this error on their site:

"We couldn’t save your cookie preferences. Please adjust your browser settings or disable ad blocking. You can access your cookie settings at any time by clicking “Cookie Settings” in the footer."

To be fair, Firefox does say this under the Strict setting:

Heads up! This setting may cause some websites to not display content or work correctly. If a site seems broken, you may want to turn off tracking protection for that site to load all content.