Background
When a Jira issue is updated, Jira sends out an email to watchers, assignee, reporter etc. 
The email outlines what has changed. When the description has changed, the complete before and after text is provided - as per the example below:

<who> updated <jira project issue id>:

-------------------------------------

    Description:

<new content of description field>
This is an important notice!
It should therefore be located at the beginning of this description!

This part of the description has stayed the same from version to version.
It shouldn't be shown if it doesn't change.

It is important to spell check this description.
On the other hand, a misspelled word isn't the end of the world.
Nothing in the rest of this paragraph needs to be changed.
Things can be added after it.

This paragraph contains important new additions to this description.

  was:
<old content of description field>
This part of the description has stayed the same from version to version.
It shouldn't be shown if it doesn't change.

This paragraph contains text that is outdated.
It will be deleted in the near future.

It is important to spell check this deskription.
On the other hand, a misspelled word isn't the end of the world.
Nothing in the rest of this paragraph needs to be changed.
Things can be added after it.

The Problem
When descriptions contain a lot of text it is implausible to discern what has actually changed from the email - thereby triggering a side by side comparison by those who really care to determine the differences.
This is a time consuming task, and it is frustrating to find that the effort is not worthwhile if the differences are small.

Feature Request
Please provide a line-by-line comparison of the description field in update emails using a tool such as Diff e.g.

0a1,3
> This is an important notice!
> It should therefore be located at the beginning of this description!
>
4,6d7
< This paragraph contains text that is outdated.
< It will be deleted in the near future.
<
7c7
< It is important to spell check this deskription.
—
> It is important to spell check this description.
10a11,12
>
> This paragraph contains important new additions to this description.

Benefit
Time saving determining what has changed and therefore if changes to descriptions are significant for the receiver.
Most people I work with are ignoring Jira update emails (with filter rules to delete them) because there are so many of them and they usually provide little value. With a line-by-line comparison of the description, the update email would become a invaluable tool for people in the position that they need to know exactly what has changed.

Stretch Goal
Provide rich text emails with colouring to further highlight if it is an addition or subtraction. e.g. TortoiseMerge or WinMerge style.