When using diff -r to compare two trees containing symlinks, and some of the symlinks point to missing targets outside a tree, there should be an option to compare just symlink target names. This is useful when comparing a restored partition backup on a temporary mountpoint. The position of the mountpoint may invalidate any symlinks pointing out of the tree. The integrity of the backup depends on the content of the symlink itself, not its target.
Yes. This is noted in "Future Projects" <http://www.gnu.org/manual/diffutils-2.7/html_chapter/diff_18.html>.