Hello,
We've noticed that Jira is playing around with the email notification templates: it is 3rd or 4th time some of the teams are switching back and forth the email templates which breaks emails grouping by ticket #.
We hardly insist on two things:
1. do not change it without proper testing the changes (we are not sanbox users that can be a testing group)
2. provide the opportunity to stick to the previous email notification templates (for the cases where any of your changes break our convenience)