Seeing Tree Style Tabs continuity halted and more importantly a developper motivation deeply affected is not a good sign for the community and users who engaged with Mozzilla's goals and with its addon community.
Tree Style Tabs empowers the user browsing activity at a level rarely seen. It brings to awareness constant history (tab tree) and allows the user to mature its browsing profile with structure.
An deeply thought addon that really shapes the browser into a navigation tool that empowers its users and allows building more mature browsing focus and improves the individual's independence.
Mozilla should review carefully the resulting loss of differentiating value by letting a valued and committed add-on developper go and how this diffuse into impacting its mission.