> as it seems bad design to have to fix and maintain a wordlist for every language as the checksum depends on it.
From BIP39:
> The conversion of the mnemonic sentence to a binary seed is completely independent from generating the sentence. This results in rather simple code; there are no constraints on sentence structure and clients are free to implement their own wordlists or even whole sentence generators, allowing for flexibility in wordlists for typo detection or other purposes.
>
> Although using a mnemonic not generated by the algorithm described in "Generating the mnemonic" section is possible, this is not advised and software must compute a checksum for the mnemonic sentence using a wordlist and issue a warning if it is invalid.
So BIP39 states "no constraints on sentence structure and clients are free to implement their own wordlists or even whole sentence generators" and yet at the same time one paragraph later "this is not advised and software must compute a checksum for the mnemonic sentence using a wordlist and issue a warning if it is invalid"...
My interpretation of this:
1. ChecksumCheck function attempts to 1. find the wordlist 2. calculate the checksum.
2. If it fails to find the wordlist, return false
3. If the checksum doesn't match return false
4. If ChecksumCheck returns false, "issue a warning" but do not block seed generation. "We couldn't check if your phrase is correct... you're on your own"
99.99% of implementing apps interpretation: (remember, error handling for userspace is not done by the BIP39 library, but the app that uses it)
1. Run ChecksumCheck
2. If False, hard fail, do not allow seed generation.
If more apps would implement to the word of the BIP39 spec, multiple languages make sense, but since reality is no one follows the spec (/the spec is way too open to interpretation) then expecting every app to load every language is unreasonable.
Electrum actually handles BIP39 recovery the way the BIP specifies. I can restore random strings if I want, and it warns me, and I can ignore it if I wish.
Anywho. The BIP39 multi-language feature is crucial for non-English speakers especially from Asia. Maybe northern Europeans have no problem with English word spelling, but watching a normal Japanese person write down their English mnemonic is painful.
One letter at a time, worried they wrote it wrong... still make mistakes... lose money because of it.
Whereas users of Copay etc. that support Japanese wordlist write down their seed easily, and I have never heard of a Japanese newbie complaining about "but I'm writing it just how I have it written down" about their Japanese seed... only English.
Not trying to give anyone a hard time, just telling the facts: lack of localized words for recovery phrase causes more money loss than supporting it. (When push comes to shove, at the very least Electrum will always support their recovery because it lets you hash anything)
This is all anecdotal of course. Just sharing my experience evangelizing in Japan.
Thanks,
Jon