For Mozilla's Bugzilla:

Merge continuous "Updated" changes / auxiliary changes created by the same author to get a much compact view.

For RedHat or KDE's Bugzilla:

Merge continuous comments created by the same user and get a much compact view too.

CSS are added and the ids are kept, thus :target highlight still works on Mozilla's Bugzilla.
And it also works on RedHat or KDE's Bugzilla too, even though they don't have it by default.

This UserScript don't require jQuery or any Web framework.