We use Email-plugin. Sometimes, for closed tickets, an email arrives to the closed ticket and its status is set to ASSIGNED, despite our config looks like this:
Look at this setting:
/**
* When a note is added to a bug currently in $g_bug_feedback_status, and the note
* author is the bug's reporter, this option will automatically set the bug status
* to $g_bug_submit_status or $g_bug_assigned_status if the bug is assigned to a
* developer. Defaults to enabled.
* @global boolean $g_reassign_on_feedback
*/
$g_reassign_on_feedback = ON;