When in Pose mode, if the armature is not in a visible layer, the Pose dropdown menu in the header of the 3D View is replaced with Object, causing a misalignment that makes layers selection uncomfortable. Further, the Object menu belongs to Object mode and not to Pose mode.
I'm guessing the misalignment you're talking about is the slight shift left to right. I think that can be sorted within the UI layout, because everything from the "Select" menu shifts slightly.
As for the "Pose" menu changing to "Object" in the header, as well as in the Tools bar:
I'm guessing as there are no selected bones/armatures in pose mode on the other layer, it'll default to Object mode. Therefore, I'm guessing it's not a bug but an unforeseen circumstance in the context of the UI layout code, or something. :)
I'll let the "big boys" take it from here. :) lol
The problem is that the context.mode == 'POSE' but context.active_object == None,
This confuses the UI layout. options are...
- have the context.active_object be valid even when layer isnt active (like editmode)
- Not draw layers (like editmode), users
- get the active object from the scene, so layers are ignored: context.scene.active_object
- Ignore this issue.
if context.active_object == None and context.mode != 'OBJECT': context.mode = 'OBJECT'
So it falls back to object mode by default. It might be considered too intrusive on the user's side though.
Getting active object from scene would help resolving alignment issue, but menu would become useless in paradigm interface sticks to -- operator operates with visible objects only. Not drawing layers wouldn't actually help since you could toggle layers with a hotkey (which ideally should also be solved for edit mode, and i believe for sculpt mode as well).
Another thing is that it's not the only place where misalignment happens -- afair we still have some issues with modifiers and some other parts of the interface.
This could be imprved, but wouldnt actually consider this is a bug. Added note to our TODO wiki http://wiki.blender.org/index.php/Dev:2.5/Source/Development/Todo/UserInterface#UI_Widgets
Thanks for the report, but closing it now.