It's really useful to be able to look at the summary of comments and click on the line number to jump to an inline comment. This doesn't work if the comment was on a revision other than the current one, though. There are two cases:

• The inline comment was on a revision displayed on the left in Differential. For example, if I put Diff 1 up and get comments on it, update it to Diff 2, and then put Diff 1 and Diff 2 side-by-side, the comment summaries for Diff 1 don't hyperlink into Diff 1.
• The comment was on a revision not currently displayed in Differential. Imagine the above scenario but with the Base revision and Diff 2 displayed. I can still read the comment summaries for Diff 1 but they don't link into it.