Understood. I think it is still useful to have a small core base that you can read and understand and adapt if you want to. Don't like the GUI open file dialogs? Someone did a text based interface:
The canon doesn't need my changes but I need the canon changes. If I change the core, I will have to selectively merge whenever updates happen. It's great that core is small and can directly be changed, but I think that should be advertised as the last resort.
http://nilnor.github.com/textredux/tour.html
No need to sync back upstream.
I agree with you that 'Unparalleled extensibility.' might be a bold and difficult to actually prove claim.