It’s just a silly pun about hentaigana having “hentai” in the name. Hentaigana is really just variants of the letters of the Japanese syllabary; the hen part is incidentally the same character as in hentai but the tai part is written with a different character.

I love that Pooh face. That’s me most of the time talking to other commies who actually read theory (or complete cranks who tell me to read it but clearly haven’t read any themselves).