Resetting zoom level changes font when "Use system monospace font" is checked
I'm able to consistently reproduce this by pressing Ctrl+0, without even changing the zoom level beforehand. I think the font being set is the one set in the font picker control located under the "Use system monospace font" checkbox, under the View tab in the Preferences dialog, even when the checkbox is checked and the font picker disabled.
I'm using Arch Linux, Mousepad 0.5.8.