I'm not sure how this would be possible, as I think it may require some re-writing of the notifications in JIRA.
However I'm finding my users are getting too many e-mails to handle the notifications from JIRA effectively. It would be useful to send a summary e-mail to the user after a set of actions has been completed to notify them that these items have changed in a certain way.
i.e in one e-mail the body would contain
JIRA-01 - Summary changed was: This Is The Title now: The New Title
JIRA-02 - Component changed was: Flange now: Sprocket
JIRA-56 - Assignee changed was: Bob Hope now: Randy Crawford