It does happen, and has happened with one of ours.  Ours is a manx with no
tail and poop sometimes gets stuck to his butt as well.  We bathe his rear
end with kitty shampoo when necessary.  He had some loose stools while
getting acclimated to his new home and new food.  It just takes time.  I'm
sure your kitty will overcome the problem.  It's frustrating, I know, but
beats the hell out of changing a baby's diapers.  Ugh!

James, before I begin, let me tell you that I do not have a remedy-- I'm in
your boat.  My new kitten has soft poop and he doesn't clean his butt.

We have two kittens.  Mia is a girl and we had her first. She's fine.
Sometimes she'll get some kitty roca on her butt (she's a long-haired cat),
but she's pretty religious about cleaning herself, and if it's really bad,
she'll let us snip off the piece of hair it's stuck to.  She is a little over
a year old and pretty independant.

Ollie is a boy and we got him a week or so before Thanksgiving last year.  He
was about 9 - 10 weeks old when we got him then.  Ollie was OBVIOUSLY taken
away from his mother way too young.  He could have been a rescue cat, I found
him on craigslist so I really don't know his history.  According to the girl
who had him, she bought him from a local petstore.  She has been promising me
his health papers for a long time but I've yet to see them.  

We took Ollie to get his first shots and he tested positive for kitty
leukemia.  Some cats are only carriers and may never show symptoms of being
sick.  He had horrible diarrhea when we first brought him home, which I guess
is normal.  He and Mia didn't get along very well for at least a month so I'm
sure that added extra stress for him.  But he was always super affectionate
(a TOTAL mama's boy; Mia on the other hand is a daddy's boy to boot).  He is
playful and is such a little piggy! ALL he cares about is food.  Still, the
poop is soft.  Not runny like it used to be, but soft.  I'm not sure if he's
learning from Mia.  They are getting along much better.  I've caught them
snuggled up together on the bed a few times. That doesn't mean they don't
mess with eachother and hiss and growl once in awhile.

Ollie has soft poop to this day, it's been three months since we've gotten
him, which would make him almost 6 months old now -- about time to get
neutered. Not sure if that should help or make things worse. I guess I'll
have to talk to my vet and see what he thinks.  They've told me not to feed
him wet food but we feed Mia wet food and there's no way to keep him from
hearing the can when it's time to feed her.  He does munch on the dry food
all day but I give him a little bit of wet food as a treat.  He's a screamer
and he doesn't ever give up is mission for food so I can't take that away.

Maybe there's some kind of wet food specially designed for kittens with more
sensitive digestive systems?

Let me know if you hear anything.

Thanks!