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.
![Smiley](https://bitcointalk.org/Smileys/default/smiley.gif)
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.