When you edit a task, you get a diff of the changes. However, when you edit a comment, you get the different versions of the comment one after the other. You must compare them side by side to see what changed.
Why not offering the useful diff view as well?
I think this gets complicated pretty quickly when there is more than one edit and that makes this non-trivial to plan and build. My concern is this doesn't actually solve any problem, other than curiosity. Edits are likely to fall into two scenarios, either minor typos, which a diff view is better, and major edits, which History view is generally easier to digest the changes.