From the Atlassian Documentation:
For each event notification, JIRA will only send the first encountered email intended for a recipient. Hence, in the case where a user is included in two or more recipient lists (e.g. the Project Lead and current reporter) for one event notification, the user will only receive the first encountered email notification. JIRA will log the fact that this user was on multiple recipient lists.
JIRA’s default setting is to not notify users of their own changes. This can be changed on a per user basis via their Profile Preferences.