Per the email from Gergo on the wiktitech-l gerrit upgrade thread, the links to Diffusion are either missing or broken in some cases.
- It is present (and working) next to the current commit sha1 (see https://gerrit.wikimedia.org/r/#/c/326543/ )
- It is missing from next to the parent commit sha1
- They are broken at the top of the diff view (eg: https://gerrit.wikimedia.org/r/#/c/326543/1/make-wmf-branch/MakeWmfBranch.php )