InlineHistory inserts bug activity inline with the comments when viewing a bug. It was derived from the Bugzilla Tweaks Addon by Ehasn Akhgari. For technical and performance reasons it is only available to logged in users, and is enabled by a User Preference. It works with an unmodified install of Bugzilla 4.0 and 4.2. If you have modified your show_bug template, the javascript in web/inline-history.js may need to be updated to suit your installation.