Who says you can't feel it?
And it still belongs to you, so using it without permission is theft.
Petitioners do not have any mental tie to their corpse. Nowhere are they stated to feel what their corpse feels. If they did, they would be in constant agony because corpses
rot. Calling it theft is, again, like calling garbage rooting theft. They've essentially thrown their body away and have no need for it.
But, again, I don't think you can point to one single reason as THE reason undead are evil. It's the combination of disrespect for the dead, body theft, violation of the natural order, using the magic of anti-life, creating creatures that might create spawn. All before you get into the issue of corrupting souls, trapping souls, and the like.
Undead are not anymore "wrong" or "unnatural" than countless other things in D&D. It's not disrespecting the dead because the dead are currently enjoying the afterlife and have no need of their corpse, its not theft because the dead person doesn't own it (although you could say you're stealing from any surviving family if the corpse wasn't sold to you), it's no more a violation of nature than creating golems or resurrecting the dead or mind-raping people or using "afflictions" or artificially crossbreeding magical creatures or countless other magical things that would be considered morally wrong in the real world. Creating spawn isn't evil, otherwise yellow musk zombies (which are plants) would be considered evil.
The rules don't say one way or another.
However, given souls are a big deal in hell, it's likely mortal magic can't easily create one. And resurrection an expensive process, which would be cheaper if you could fabricate a new soul. This is logically backed up by the spells trap the soul, designed to prevent resurrection magic. It's an 8th-level spell and if someone could just create a new soul via the 6th-level spell create undead it would be silly to try and trap souls.
I think it's fair to say that mortal magic cannot create souls.
Creating a soul from scratch and calling a soul from the afterlife are two different things and are in no way equivalent. It's like saying that your three year old computer is identical to a new computer with a different OS installed. It would be pointless for hell to create souls from scratch, since those souls wouldn't be inscribed with a lifetime of evil deeds (although the extraplanar animals and humanoids native to hell apparently aren't considered sources of evil souls). That's assuming that the "souls" created by Create Undead are in any way similar to the souls of formerly living creatures, as opposed to being qualitatively different kinds of souls that aren't affected by resurrection spells.
Plus, souls contain the memories of the person in D&D. And intelligent undead retain the memories of their past life.
So it's a very safe bet that intelligent undead would have to have the same soul.
No, actually souls don't carry any memories. Petitioners have no memories of their former lives. Corpses
without souls retain their memories (as stated by
speak with dead). So if you placed a completely new soul in a corpse, it would logically have all the corpse's memories, but wouldn't actually be the same person (since the original soul is in the afterlife).
True resurrection implicitly recreates the memories from nowhere if there's no corpse to use.
I was reading the test of the
resurrection and
true resurrection spells, and I noticed that the common assumption that being undead prevents resurrection is not actually supported by the text. If either of these spells are targeted on an undead,
or the corpse of an undead, it becomes the living creature it once was (as stated by the undead type description, but not the spells), but it can't be used to resurrect a formerly undead corpse back as the undead creature it was before (as stated by the spells). In the case of
true resurrection, there isn't any indication that the existence of an undead prevents the original person from being resurrected. This seems to be based on a misinterpretation of the text, which is actually stating the previous (it works on an "alive" undead creature or the corpse of an undead), to differentiate it from
raise dead (which is nullified if a corpse was reanimated as undead at any point, regardless of current condition; although this
isn't actually stated and you could easily interpret that destroying an undead makes the corpse available for
raise dead). The wording of these spells is just poor and ambiguous, IMO.