When messages flash up in the graphical UI, they also seem to show up in minimised, corrupted format at the top of the embedded ASCII minimap.
I assume from this that the minimap is just a miniaturised version of the main screen rendered in ASCII rather than tile graphics - but I don't remember seeing this happen in previous builds, and no other UI component does this.
Noticed it first when auto-walking and auto-exploring. Each time my character stopped short due to an interruption white and black garbled lines would flash at the top of the smaller insert.