He’s as blind as a bat.
It is an expression. Ok. But if I were to introduce the new cloze word “talpa” , I would translate it as a “mole”, which coveys the same idea in this sentence. So, in my new vocabulary “talpa” would not be flying and “pipistrello” would not be sitting in the ground.
I totally agree.
Since the expression “as blind as a mole” is also known in English there is absolutely no reason for confusing the learners.
BTW in German it is also the mole: “Blind wie ein Maulwurf”. In cartoons for children a mole is often wearing dark glasses and a blind man’s armband.
This Tatoeba sentence was translated from English, and I appreciate that the translator didn’t translate “blind as a bat” literally as “cieco come un pipistrello”, or “come un mazzo” 
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This Tatoeba sentence was translated from English, and I appreciate that the translator didn’t translate “blind as a bat” literally as “cieco come un pipistrello”, or “come un mazzo” .