The fact that your parma drops by 3 when you extend it to someone/thing is a pretty big deterent for putting it on a horse while your out fer a ride.
I'd always read it that you need to extend your parma to your apprentice while they are working in the lab with you, or some other activity where they may face magical danger. This is more to protect them from magical accidents then anything else. The rest of the time it doesn't really matter
There is still no declarative statement that says Parma blocks the effect of the Gift to the non-gifted.
Only people with the Gift can learn Parma Magica.
Any time it is mentioned that Parma is extended ,
the only references are to Magic Resistance.
The only specific case where Parma blocks the effect of the Gift
for someone who has not learnt Parma ,
is with an Apprentice.
Nor is there to the opposite. I find that since your interpretation is more specialised (that this only goes for persons with the Gift), it should and would have been specified if such was the case. In short I think your take is an interpretation of the Parma, even if it might be a reasonable house rule. Moreso with the current focus on the parma's use as a loophole.
Whereas it might be very reasonable to protect the apprentice toward 'accidents' in the lab, the passage that require you to share your parma with your apprentice actually states that this is because he has to be shielded from the bad effects of the Gift. The motivation probably being that the apprentice is not being trained properbly (as is his right) if his learning is distracted by his masters Gift.
Well, it looks like we may have to house rule the willingness of the participant as that completely slipped our minds on a couple occasions. The gentle Gifted magus of the covenant has on occasion discretely passed his parma on to visitors to the covenant to negate the effects of our more blatantly Gifted members. (Because it doesn't do to creep out the Bishop of Toulouse when you're covenant is knee-deep in Cathar country.)
I think there are significant drawbacks to extending parma to mounts (namely the reduction of its score) that it would take limited abuse. You certainly wouldn't be riding these mounts into battle. But perhaps the willingness is such that only a gentle Gifted magus could do it at all.
Could someone post the question to the Berklist?
I would have already done so to get extra feedback ,
but none of my posts are getting through.
No need to house rule it - the RAW specifically states that the shielded must consent to the parma.
Right. And that's the part I'd have to house rule because those individuals (and the theoretical horse) did not consent.
While I think the answer for my troupe will be Door Number B, I love this idea. This would be a great flaw, if nothing else.
I always imagined having to recast your Parma...
As for puttin your Parma on a stranger...do you think someone would allow that creepy guy to cast a spell on him???
..part of the effect of the Gift...they don't trust you.
The rules actually only specify to things: consent and just touching... ( 
) and nothing more.
Which is why you have the gentle Gifted magus do it before introducing the rest of the creepy crew.
Which is why its a Major Virtue...
Still, a complete stranger wants to cast a spell on you..."To help you"
Nice guy or not...would you trust him?
Kind of like leaving your bank after withdrawing money, and a complete stranger walks up and offers to carry your wallet because it MUST be heavy...
That's what I originally meant. However, the apprentice argument is swaying me away from it, somewhat.
Hm. That's a 3rd edition holdover, isn't it? Or do you have a modern reference? Interacts somewhat strangely with the idea that places with a Magic aura feels more real, has brighter colours, etc. ... but could certainly fit.
Hmm. Serfs Parma, but dont think that there is such a reference so for now I gladly admit it to be outside the scope of 5th RAW. We just use it because we like the idea and we impart on it no rule mechanic importance - only description and ingame setting. And the effect is really very vague - but certainly enough to make the food crazed magus keep it down during eating and enough to use to describe a somewhat growing sense of detachment with the troupe's somewhat paranoid magus with a very high parma.
I am not certain of your argument of magical places. They exactly seems brighter and more real because of the magic aura - and since the parma shields off magic, it fits very nicely that this shielding somewhat numbs the senses a tad bit to the world. The parma isn't magic (well of course it is!), it is more of a barrier against magic.