Quote from: HCP on March 18, 2021, 10:10:57 PM

So you are effectively reducing your security to "only" the security of a standard bitcoin private key...

Even if he did write down his 600 word seed and never looked at his private keys, his security is still 128 bits. It doesn't matter what ridiculous thing he does with his seed phrase; his keys will never be more secure than 128 bits.

All these things you can do your seed phrase - force it to be 600 words, additional passphrases, etc. - might increase the physical security of your seed phrase if it means an attacker has to compromise two or more back ups instead of just one, but the cryptographic security of your private keys remains 128 bits.