« bugzilla inline history extension
Unlike most bug tracking systems, Bugzilla doesn't display changes made to fields when it displays the comments. This has been a often requested feature, and is currently targeted for Bugzilla version 5.0. For some time the Bugzilla Tweaks Firefox add-on has provided this functionality to bugzilla.mozilla.org, and it's working well for those who have discovered this add-on.
Using the Tweaks implementation as a guide, I have implemented an Inline History Bugzilla extension:
This extension has just been deployed to BMO and is currently disabled by default. To enable you have to be logged in, then go your User Preferences, and set When viewing a bug, show all bug activity to on.
Once we're happy with it it will be enabled by default for all logged-in users. [Edit: Now enabled by default]
The latest version of Bugzilla Tweaks (v1.11) will detect when this Bugzilla extension is active, and will disable its inline history implementation. The option to disable the extension will always be available should someone perfer Bugzilla Tweaks' formatting over the extension's.