Also avoid lowercase rn which can be mistaken for m.

And avoiding vowels can help avoid offensive words within a generated code:

FUKFUK9 - https://www.replacements.com/china-fukagawa-fuk9/c/27446

KUNT1 - https://id.made-in-china.com/co_gzberlin/product_Power-Steer...

base32 removes the I,O,U but other words with A,E need to be avoided too - no vowels helps avoid words in English.