Quote from: larry_vw_1955 on Today at 02:07:32 AM

it's only guaranteed to detect up to 4 "substitution errors". a substitution error would be when you replace a g with a q maybe. i guess that's what it is. probably the most common error but still. the statement needs qualification.

What other errors are there? Bech32 addresses are of a fixed length (42 characters for P2WPKH, 62 characters for P2WSH or P2TR), so any error which adds or deletes a few characters will immediately result in an invalid address. The checksum will detect any error which affects up to 4 characters.

Quote from: larry_vw_1955 on Today at 02:07:32 AM

there can't be any other reason.

The reason that Bech32 excludes the characters "1", "b", "i", and "o" is explained in BIP173:

Quote from: https://github.com/bitcoin/bips/blob/master/bip-0173.mediawiki#cite_note-4

The character set is chosen to minimize ambiguity according to this visual similarity data, and the ordering is chosen to minimize the number of pairs of similar characters (according to the same data) that differ in more than 1 bit. As the checksum is chosen to maximize detection capabilities for low numbers of bit errors, this choice improves its performance under some error models.