This fuckin thing just appeared unexpectedly. Does anyone know where the setting to get rid of it is?

Settings shortcut: Comment options > Display navigation bar

Click on that 👆, it will take you to the setting that you need to turn off.

Ooh, I like being able to jump from top comment to top comment. Imma go enable that

Probably not using the same client, but there might be something related to "floating button" or a setting in comments appearence.