Thunderbird message fonts

I was getting really irritated with my attempts at changing the font size of message renders in Thunderbird. I was doing what appeared to be the right thing: Hamburger menu > Settings > Language & Fonts > Advanced ... and then set family and sizes as desired:

Notice that "Latin" is selected in the Fonts for: dropdown. This was the default setting, and given the other choices (Arabic, Armenian, etc.), it seemed to be the correct option. But nada.

Fortunately, a statement made almost in passing on this post revealed the solution: You need to configure "Other Writing Systems" as well:

 

Why? Because "Other Writing Systems" deals with Unicode encoding, and because it's 2025 you're probably sending and receiving Unicode messages.

It's easy when you know how.™ (But almost impossible to discover.)