Symptoms

When the user log work on the issue, an notification will be sent out as issue updated.

Even in the notification schemed is configure to have no notifications sent for all the work log event.

This is replicable in the latest OnDemand release 6.4-OD-11-012

Workaround

Disable the issue updated notification will prevent the notification sent for work logging event but of course no notifications will not be sent when issue updated as well.