By making an official statement not only would Open Pandora have to take good faith and user/manufacturer discretion out of the equation, but they'd also have to break the habit of a company lifetime. If they make an official rule, in the interests of absolute fairness it would then have to be upheld. And it would also have to be harsh - to guard against imbeciles they'd have to put EVERYONE off opening up their pandora, and that would mean a lot of sensible people would probably lose out on what has been great and sensible support. Perhaps you could ask more discreetly so the answer you receive won't have binding repercussions for us all.
I don't mean to sound like a dick, it's just that it seems to me they treat people very fairly. Unless you open up the Pandora and clearly damage something through carelessness, they are likely to overlook non damaging mods to the hardware (like shoulder button mods, if you destroy the shoulder button doing it they won't fix that for free, but if the screen failed due to something unrelated to that mod they will most likely have no problem). The official answer must be assumed to be "Don't open it, if there are any signs you opened it warranty is void". This is what they would be bound to say for fear of financial repercussions, as the situation stands any ambiguity is protecting us more than them.
I think the "official" ideology is this is an "open" device. Just be sensible and DON'T try to abuse the system. So long as you are comfortable opening up the device to make minor mods, and you are also competent then you can be confident that unrelated issues will be dealt with. If you are unsure in any way, DON'T risk breaking things. If you need a clearer answer from someone official (unlike me, I'm mere lowly scum) perhaps send someone with authority a PM.
EDIT: Craig obviously feels ZXDunny is not an imbecile with no experience (bet you're glad to know that ZX). I'm certain he wasn't suggesting EVERYONE is capable of fixing their own devices.