Haha, I noticed that and edited it out. I had posted this to Reddit as well, and I copy-pasted it here.

Very interesting. This looks fine on my Firefox Nightly for Android application. I wonder why it renders differently on different versions of Firefox alone.

Ah, I apologize for not documenting the quit key correctly.

The quit keybinding has been an issue (albeit a very silly one), which could be easily corrected, but somehow escapes my attention during the release phase. I will correct the documentation.

Do note that since the keybindings are customisable, you can modify the quit behavior to a keybinding of your choice. See the “Configuration” section of the documentation for more details.