1. Create differential revision.
2. Add several comments and submit.
3. Scroll to timeline on revision page and click a comment to be taken to the code location.
4. Use back-button to return to the timeline, but scroll position on page does not change.

This would be useful when a revision contains large changes or numerous files.

I see the updated comment header has up/down arrows to navigate (I haven't thoroughly tested these), but the desire to return to timeline of comments is usually so I can review newer comments which are not necessarily adjacent.