As above.
Magi are often under mystical effects like the longevity ritual or the familiar bond, which means they should penetrate to be able to touch other magi.
Even ignoring that, parma is itself a mystical effect and lacks an explicit penetration score- i presume no penetration at all.
In all cases, the effects given don't have a known penetration. So do magi have to penetrate to touch one another, and if so how to adjucate what that penetration is?
For things like longevity rituals or familiar bonds they should probably be treated similar to item effects - zero penetration unless someone explicitly and deliberately added penetration to them.
It's not completely clear cut (and I can certainly see arguments for why it should do), but I wouldn't require someone to need to penetrate just because they had a Longevity Ritual or Familiar Bond - it feels like the sort of thing where if it was the case, it would have a significant impact on the setting that would have been flagged a lot more prominently. After all, "everyone over a certain age has a Pen 0 effect permanently on them" is essentially "none of them can ever cast any Touch range spells on anyone with magic resistance".
It does feel like itd be mentioned, especially with magi canonically having had children with other magi- however at the same time, this would contradict the rules set.
If you are under a mystical effect, you must penetrate to touch others. Thats really it.
Now one could argue they flub this by using Part Target so the mystical aspect isn't on the magus' body, but that isn't explicit and is unlikely since iirc the familiar bond can boost physicality.
Also parma is still a mystical effect even if the longevity ritual and the familiar bond didn't need to penetrate, which is already questionable.
Edit: also, in DE parma, longevity ritual and familiar bond does have to penetrate to enter the aegis providing the aegis penetrates the magus' MR. However, the longevity rityal and the familiar bond renews itself immediately after going through the aegis' boundary- so it does technically need to penetrate in one specific aspect at least.
This question has been discussed before here: Yet Another Parma Magica Question - #3 by Vortigern
Project: Redcap has a pretty good page on MR: Magic Resistance - Project: Redcap
I'd rule that LR, Parma and familiar bonds don't count, because that would give strange results. For characters under spells, there is a clear rule in DE: "An invisible character cannot touch or exert physical force on the maga, even if the invisibility spell had Personal Range."
Where can I find that rule?
In the description of the Aegis in DE.
One of the reasons talismans are handy 
But yes, that's how we play it!
... unless they penetrate it or their Target drops it. Is this really that terrible for magi over 30+ years? There are lots of other Ranges for attack spells anyway.
Do you rule that the attunement doesn't count as meaning a talisman needs to penetrate, then?
But if it's Pen 0 they won't penetrate it unless their target drops their Parma. So no Bind Wounds or Purification of the Festuring Wounds on your unconscious friend, for example.
Unconscious because of Fatigue goes away after a few hours or a night's rest. Incapacitated because of Wounds should not prevent one from dropping ones Parma. ReMe Snap of Awakening is logically R: Voice.
Bind Wounds doesn't benefit an unconscious Target, while Purification of the Festering Wounds provides a long-term effect. So both usually make little sense to force upon unconscious Targets.
But if one has learned these healing spells as described, a variant of ReVi Opening the Intangible Tunnel like Voice of Healing R: Voice, D: Conc, T: Ind is typically easy to learn or invent at level 10 for magi of age over 30+, and allows to cast such spells at R: Voice even on inconscious sodales.
Dropping ones Parma requires a (not so easy) Concentration check, which would suffer from the Wound penalty making it even harder.
If you have an Incapacitating wound, you can't do anything.
When you snap your fingers you instantly awaken the
target from sleep to alert consciousness. Does not
work on someone unconscious from Fatigue-level
loss, wounds, or magic.
Snap of Awakening explciitly doesn't work if the unconsciousness is caused by wounds- which is usually the case for Incapacitated. You could awaken them for other reasons, presuming it isn't due to lack of fatigue or magic.
Dropping parma doesn't require a check- keeping parma dropped does. But characters do have a grace period of 2 minutes presuming nothing happens like getting stabbed where they're able to keep parma dropped without issue- unless one's SG is strict and says being wounded earlier is enough to trigger a roll.
We have (ArMDE 07-Hermetic Magic): "A magus can suppress his Parma by concentrating, and this also suppresses his Form resistance. This suppression lasts for as long as the magus concentrates, which takes the same effort as concentration on maintaining a spell, and leaves him with no Magic Resistance against anything." Since the healing spells in question are cast in a standard action, dropping the Parma over that time does not require a Concentration roll AFAICS.
Roll or not, you can't do anything while Incapacitated. Which should include concentrating.
Yep. That is why I treated Unconscious from Fatigue and Incapacitated by Wounds in my post separately before.
Sure, but wound penalties of less severe wounds are a non issue in this specific regard.
It was loose wording on my part - I meant Incapacitated.
I am confused then- how would Incapacited not prevent one from dropping their MR? They're unconscious, they cannot concentrate.