Steps to reproduce: (requires you to be sysop)
- Find two consecutive non-patrolled edits (you can also make them yourself by logging out first)
- Click on the diff link for the first edit (in recentchanges).
- A [Mark as patrolled] link appears.
- Click Next diff->
- There is no [Mark as patrolled] link.
- Click <-Previous diff
- The [Mark as patrolled] link you saw in step 3 has disappeared.
More precisely, the problem here is that the rcid isn't passed when using the next/prev links. Wouldn't it be possible to just look up the revision ID in the recentchanges table rather than using the rcid? This would make [Mark as patrolled] links for diffs from the History or for combined diffs possible as well.