The Greek that is translated as «fool» (in Matthew 5:22) or «insane» is translated in Mairasi as «(your/their) vision has dried up.» The opposite («sane») is «vision is well-split» (see right mind / sound-minded).
In Elhomwe it is idiomatically translated as «not grasping the head.» (Source: project-specific translation notes in Paratext)
See also You are out of your mind!.