@DeepWolf Most Friends are illiterate. See the hallway and the light switch for an early example in this story (Ch. 15). The Otters see markings on the wall and try to determine what the marks mean.
Most aren't familiar with the English language either, but the elevator girl knew enough to say "Don't touch me!". The original English is denoted by a different font. The main human explorer, "Gachi-Oji", speaks English. Arai-san has no idea what he was saying when they were in the elevator together.
If the Otters misspelled anything, it would be character appropriate.