Anyway, the BIP32 spec explains all this.
Yes. But all that cryptomagic is so far out of "normal world expectations" that most people won't consider this. And I can't blame them.
I understand. Alas, the original question was, "Is the seed weakened if you post some private keys?" Sure, in an ideal world, one could give a layman's explanation that would satisfy everyone. In the case of BIP32, I'm not entirely sure it's possible, at least not without spending a lot of time thinking about a good analogy.
Anyway, when the original article was posted, stating that BIP32 has a massive flaw, I responded with a somewhat technical answer that partially negated it. Not as much as I'd like, granted, and certainly not in layman's terms. I still felt the need to point out that the article didn't tell the whole story. The article was somewhat technical, so I was somewhat technical. If people can read and understand an article that points out how the math in BIP32 is flawed, they can read the original spec.
All wallets should bump a fat red flashing warning explaining this in few words whenever a master key or a private key is displayed, exported, backupped or printed. Well, once at least.
I will simply not export or communicate *anything* from my wallet except public addresses.
I agree that a simple but large warning is appropriate. Any time you move private keys around, you're taking a risk. A measured risk, perhaps, but a risk nonetheless. Caveat emptor and all that.
