The reason it doesn't mention TA-082's is because the TA-082 downgrader was released a few weeks later.

I don't blame your friend either. It's always the way when you have a new PSP; you don't want to risk losing it. I can understand where he and you are coming from, but the fact of the matter is it's 90% safe; the only thing that could brick it is user error.

IdStorage change is permanent. There has not yet (nor will there probably ever be) an firmware update that touches that area.
The IdStorage is root-level stuff; it's much like the BIOS on a PC. Updating or downgrading will only ever touch Flash1, Flash0, and the IPL.
If it touched IdStorage, you would effectively ruin any chances of recovery. Plus, there's never been any need to touch IdStorage for a firmware update.

In summary, your friend's IdStorage, should he choose to run the changer, will permanently become able to run any firmware. Though, it is crucial that he doesn't do this if he doesn't want to. Being encouraged and then failing is much worse than simply making him make his own decision.
Besides, if he's on 1.50, he can emulate 3.03 in Devhook and have most features anyway (PS1 emulator doesn't work).

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