Didgee, I think that is an interesting distinction, and I think you're onto something there. It brings to mind that the word "chronic" is used in regards to feelings of emptiness in description of BPD symptoms. It's an on-going perception.

The feeling you describe in depression resounds with me. It sucks.
There is just so much nothingness. Especially with anhedonia.
But we ride it out, and it goes away. TG.