"Oh great, another discussion on multi-level notebooks." Your comment it's the proof that a lot users are asking for this feature.
Just for the record i'm not asking the feature... i just want to know why Evernote refuse to listen the users....
"Evernote generally doesn't comment on these questions. " - Yes i know... they even block comments on the blog posts...
"Please provide details on how this would be done?"
Right click Over notebook name->Create Sub-note. It's too hard for you to imagine this ?
I can also provide you a data model to implement a mult-level hierarchy.