When I save an image to iOS device, the userComment field is not saved

[SarveshSub]

When I write something into the userComment field of the EXIF data (in my case, a string containing a URL I am trying to use as the key in a hashmap), and then save this file to the photo gallery on iOS, the userComment field isn't saved. I print the EXIF attributes before and after saving the image to the gallery, and in the post-save print statement, the userComment field simply is not there.

Is there any way to fix this or is this woven into the design of iPhone? Thank you.