in the Church... is no longer a glitch, it was definitely intended by the programmer.
How?
The Zack's Ghost in AC:
http://img.photobucket.com/albums/v1...hotographs.jpg
For those who can't see Zack in the photo.
There, it should prove that it definitely is Zack.
After I have been spending some time thinking about why Zack appeared in the photo. There has to be a logical reason for him to appear in the photo because there are so few unanswered questions left. Actually it could be because of Cloud's mentally stability - he's a clone, cloned by Zack. And Zack was Aeris's girlfriend. Cloud's flashbacks contained Aeris and Zack most of the time. Those two were very special moments for Cloud, I mean Cloud has special bonds between Aeris and Zack, obviously. So in Cloud's mind, he can see Zack or Aeris sometimes.
However, I now believe that the Aeris appearance inside the Church of the Final Fantasy 7 game is no longer a glitch to some extent. I believe that the appearance in the Chruch was indeed Aeris's ghost as intended by the programmer.
Although, the Aeris's Ghost appearance has occurred before she died, but perhaps that was meant to be a prediction for Cloud because like what I said, Cloud was cloned and has special bonds with Aeris and Zack, Aeris is very special OR only that part is glitched (Aeris's ghost appearing before she died) BUT I don't think the whole part of that appearance is glitched because FF7 is ALMOST flawless, why only the ghost that was glitched? So, Aeris being a ghost in the Church after she died and Zack being a ghost in the photo makes it perfectly sense. If I believe this theory, then the ghost of Aeris is not a glitch I'm pretty much convinced about this.
Oh, another evidence - Cloud saw Aeris and Zack in the light near the end of AC.
I know you would get scared if you see a Ghost.
Cloud didn't get scared when he saw Aeris's Ghost in the Church, he would have said something like "Whoa, Aeris! Where did you go!? What... she disappeared" but he didn't, which would increase the proof that it was a 100% glitch. BUT he didn't get scared when he saw Aeris and Zack's ghosts near the end of AC either. So that should prove that maybe it wasn't a glitch after all.