Do Hermes Portals and Mercere Portals inflict Warping (ok, except to the caster etc. etc.)? It really seems like they would, being 15th magnitude effects... On the other hand, it seems like a single Portal (at least a single Hermes Portal) would only inflict a single warping point to an individual, no matter how many times it's used (unless one somehow managed to remain for an extended period "in transit").
A flying carpet does not inflict warping on its passengers. Nor would an Hermes Portal for the same reason.
The "flight" effect of a flying carpet affects only the carpet. So you are saying that Hermes Portal does not "transport" things, but instead kind of "warps space" creating something like a "wormhole"? Hmm, that would be a possibility. But ... why Rego Terram then?
Yes. And they inflict Warping each transit.
It's a reason to walk.
How so? Each spell should warp you but once, unless you are subject to it for an extended duration, at least a season.
Would you also assume that the Shrouded Glen warps a passer-by each time he (re)enters the protected area, even if he does so, say, once a week?
Isn't avoiding Warping the whole reason to bother making a Hermes Portal every year instead of just enchanting a ReCo device with unlimited uses and saving the Vis?
I can do without long distance telportation at all, but that's neither here nor there discussing RAW.
HoH:TL (p.80) seems to suggest that Portals (ok, Mercere ones) are preferred to ReCo devices because they are particularly "efficient ... for trade and mass travel". So it seems to be an issue of "bulk transportation" rather than one of warping.
Trade and mass travel, huh? That's about as medieval as transatlantic air travel. Did I mention I hated long distance teleportation? 
A high magnitude spell/effect warps you each time it affects you (unless you cast it, etc).
Yes.
As I understand it, Portals work by binding stone roads together as if by an arcane connection. Its closer to Regio boundaries or trods than to straight-up ReCo effects.
Also, Mercurian portals are not strictly integrated into Hermetic Magic; they're a Mercurian holdover whose methods are not entirely understood. My understanding is that they don't cause warping, but the permanent ones are rare and cannot be made, and the year-year ones are expensive (30 pawns of vis for a pair.)
House Mercere charges tolls on use of the portals, and you still have to walk from the portal to where you want to go. Temporary portals are expensive enough to be prohibitive for casual or occasional travel.
Hermetic flight can be fast enough to meet most travel needs within the scope of an average covenant. Wings of Wind (Cr(Re)Au 30) achieves a max speed of 40 mph, and can be instilled into a small rowboat or something similar.
I've always considered that they warped the place they were cast at instead of the people using it, and that was their big advantage. So yes, I'm of the wormhole crowd 
As far as I can see, this is supported by the RAW (noble parma here: I assume warping is inflicted on the Target of the spell, but I may be wrong), since the Target of the spell isn't the person using the portal but the portal itself. That's, to me, THE difference between ReCo teleportation (Target: your corpus) and Mercere Portals (Target: Terram).
I agree with The Fixer's argument regarding Targets: since the Target is Terram, with not even a casting requisite of Corpus, then the portal does not warp someone going through it. It must somehow affect the Universe itself rather than what passes through it. It also explains why you need a portal at each end and can't just build a (one-way) portal at a location with only an Arcane Connection to the other.
But its target isnt "you" and its Form isnt Corpus and as such shouldnt affect "you".
HP is just a door. They do not warp anything but the wall where they are placed. Shrouded glen OTOH would warp anybody in them since it is a mentem effect, so the target is clear. We prefer to HR that it warps the area, though. Haunted forest and the like
Cheers,
Xavi
They shouldn't cause Warping to people passing through them, no. They are a Rego Terram effect because they are constantly controlling the location of each side of the gate. So the gates should get Warping Points, 5 every year. Also, keep in mind that House Mercere almost always stations a Redcap with every Mercere Portal, to collect tolls and to protect it.
(Edited for clarity.)
I'm with The Fixer here, too.
In reply to permanent vs. year-long ones, year-long ones should cost House Mercere 16 pawns per year for a pair, not 30 pawns.
Chris
Certainly, I can see that if you think that Portals don't affect the people using them, then they don't warp the people using them.
For me, the acid test is, does the Portal effect need to penetrate the Magic Resistance of the character moving through it?
As I read the RAW, if an effect needs to penetrate your Magic Resitance, then it affects you. According to RAW effects that affect you cause Warping.
The commentary in the Hermes Portal description about it being possible to throw unwilling people through the Portal, implies that the effect needs to penetrate your Magic Resistance.
Can you unwillingly be thrown in a regio, and should Magic Resistance help you?
I suppose so, and, no probably not. Unless you are being thrown into the regio with a Hermetic spell effect, in which case the spell effect would be resisted. Which is the problem with your analogy. You are trying to compare apples and oranges.
Hermes Portal is a Hermetic spell effect. Crossing a regio boundary is not (generally).
I think you would be hard-pressed to satisfactorially explain why Magic Resistance does not resist Hermes Portal, while it clearly does resist things like Crystal Dart.
A magic carpet is a hermetic spell effect but your MR does not affect it. Does RAW allow HP to be a hermetic spell effect that creates a regio between the 2 end points,or some other metaphorical flying carpet?