http://forums.mozillazine.org/viewtopic.php?p=11927879#p11927879
"UPDATE: I have tested the add-on for compatibility with SeaMonkey. It appears to be fully compatible, so I've uploaded a new version of the add-on which specifies SeaMonkey compatibility as well as Thunderbird compatibility. The text above has been updated to reflect this. Enjoy!"
https://addons.mozilla.org/addon/enhanced-priority-display/
Version 1.1 Released April 23, 2012 60.4 KB Works with SeaMonkey 2.8 - 2.12a1, Thunderbird 2.0a1 - 14.0a1
Compatible with SeaMonkey. Add "About" tab to preferences with copyright, contact and donation links. Add add-on icon to the install package so it'll be displayed in the UI.