"A Criamon magus's stigmata...cannot be removed, even by magic (HoH: MC, p. 50)
My question is a simple one: Can a Criamon use Imagonem magic to disguise or would the stigmata still be visible?
Or could a MuMe effect change the onlooker's perceptions?
I assume MuCo doesn't work because MuAn doesn't if the magus shapeshifts into an animal.
In other words: Is there any chance for a Criamon to visit a mundane settlement without having to face major problems?
Sure.
That's also a possibility.
Certainly. Depending on the location of the stigmata, mundane methods such as makeup or bandages and such could also hide them.
I think letting MuIm hide the stigmata cheapens it. I'd let MuMe hide it, though. I'll also let any mundane means hide it, such as cloths (or CrAn-ing cloths...). But not direct magic.
And why would clothes cover it and CrIm be unable to cover it? 
Xavi
Of course you can, but, but, it's not... apt.
Apt?
If she covers them, it's inapt.
If she doesn't....
Weed ex Criamon, and Lucky Luke ex Flambeau go shopping in town. If Weed doesn't cover her stigmata - she can't avoid violence, because Luke is itching to use his PoF to roast some mundanes in order to protect her.
So being Criamon means sitting in a cave?
Unless you are on the Path of Strife - which is the only path I really don't like.
I'd rule that MuCo cannot get rid of them (as this seems exactly what it means by "magic cannot remove them") but Mentem and imaginem magic certainly could.
You also need to think about where your stigmata are, not all magi have stigmata on their faces. One of the criamon i played started with stigmata along his chest, back and arms and it only spread to his face after progressing along his path. When in public he uses minor MuIm to avoid scaring the mundanes.
It's MAgiCK. It's not supposed to make sese 
Personally, I would allow Imaginem or Mentem to hide stigmata (because such magics are only temporary disguises), but not Corpus because that Art does effectively remove them. YMMV.
Of course not. It does mean going out in public creates risks and stories that you can deal with in a sideways Criamon way, which is presumably what you want since you're playing one.
Also, does it say somewhere that temporarily disguising your stigmata is inapt? Apt action seems to be more of a larger moral issue rather than specific injunctions against certain types of behavior. Covering your stigmata is probably perfectly fine, especially if you're meddling to make the outcome of some mundane event more apt.
If you don't want a story about what happens when you kill a bunch of mundanes, don't play a character who kills mundanes, or don't go shopping with him.
Yes, but that's not an apt act, in most paths. The stigmata are more important than your trivial daily concerns.
Given that you have the Gift, like most magi, no, not really. You are paying the price for your understanding, after all. Get some companions, and get them to do it. That's what most magi not covered with stigmata do already.
So, Luke has Gentle Gift?
My point is that magi can't really interact with society easily anyway. It's not about sitting in a cave, but it is about the idea that most magi really do need people to interact with mundanes for them.
Your answer is better than mine, of course. The point I was trying to make is that covering your stigmata is a profound thing: not a trivial thing, and that its a matter of serious moral consideration, not simply a matter of needing to fit in as you nip down to the shops. There are a couple of saints who pray to hide their stigmata, and one of them gets it granted, because for her her stigmata have become a source of pride and so she asks that they be hidden so that she can suffer in secrecy. So a Criamon in a similar storyline might be able to pull that sort of thing off.