When editing a post and using the image uploader, any unused link references are completely removed.
For example, this post has three image references, only one of which is used (
) in the body of the post:
After uploading a fourth image, references
 are completely removed (and the remaining references are renumbered to become
I sometimes write link references before using them in the body of the post and sometimes remove images temporarily before reinserting them elsewhere in the post so this is inconvenient.
(Note: this also applies for the iOS app, having the same behavior)