Message font size too small

I am not sure if this is by design but if I open a longer message (more or less any message that contains at least one or two cited original messages) then the app renders it in a totally illegible (i.e., too small) font size just so that the entire message fits to the available screen space. Please bear in mind that this happens even with "Auto-fit messages" being disabled (Settings > Global Settings > Display > Auto-fit messages). It doesn't even matter if in Settings I choose message body font size to be "200 %" because the app will still use that incredibly tiny font size for longer messages.

Strangely enough, if I rotate the phone and it switches to the landscape mode then the message font size immediately increases (though it will revert to the tiny one if I rotate the phone back). I can only guess that the algorithm estimating the "proper" font size depends significantly on available viewport width.

Shorter messages are displayed normally, i.e., any decrease in font size is not that pronounced and thus the text remains legible.

Would it therefore please be possible to set K-9 to respect some reasonable minimum allowed font size (or perhaps the respective scaling factor)? This could be definable similarly to the current options regarding font sizes of various parts of the UI -- e.g. "Minimum allowed message font size: small". In other words, the font size could decrease for longer messages but only up to a point beyond which the font size would not decrease any further.

Alternatively, the message font size (or, again, the respective scaling factor) could be fixed no matter the actual message length.

Either of these two solutions would be acceptable because it would mean that I would not have to (a) manually zoom in after opening virtually every email I get or (b) look for a magnifying glass in my drawer. ;-)

Thank you.

Android version: 5.1.1
Device: Sony Xperia Z1 Compact

Start by reproducing the small-font behavior on the reported Android setup with long messages, cited original messages, Auto-fit messages disabled, and portrait versus landscape orientation. No source files or tests are named; done means long messages retain a legible minimum or fixed font size without requiring manual zooming.