Summary

Editing a comment does not generate any change history for the issue. (Also verified from the database changegroup and changeitem tables)
All of the issue tabs (All, History) does not show the Comment Edited action.
Note: Comment Edited notifications are still being fired correctly.

Steps to Reproduce

1. User B creates a comment on ticket
2. User A edits user B's comment
3. User B receives email that user A edited user B's comment

Expected Results

User B views 'All' history tab within ticket and sees record of user A editing their comment, along with the changes made.

Actual Results

User B views 'All' history tab within ticket and sees no record of user A editing their comment.
In fact, it shows that User B's comment is now the edited comment.
See [^CommentEditNotShown.png]

Notes

Tested on 6.3.15 and also managed to reproduce the same problem.
You don't really need the mail server set up, just edit the comment and the problem is reproduced.

Workaround

No workaround at the moment.