The Feed link at the bottom of the Bug List page created from "View Bugs Reported in the last xx hours" contains actual dates in the from and to fields so any feed created using this never sees any new bugs. If the "View Bugs Reported in the last xx hours" links on http://bugs.gentoo.org/ were changed to use relative time fields e.g. chfieldfrom=24h&chfieldto=& This would seem to fix the Feed link on the generated Bug List too.
Is Bugzilla able to do this?
It has now the value 'Now', that should fix this issue. Thanks for reporting!