I am not sure what you mean. Let me restate clearly, maybe that helps:
1. User can set and adjust the mood as often as they like
2. You can sort your feed to show above or below a threshold mood. Example: Show me all notes from npubs who make me feel neutral and above. Or.. show me only notes from npubs who I consider high signal. 
3. Everyone starts at neutral so you don't need to do a lot of work and just tweak the ones you like or as you come across over time. 

I suppose you could do much of the same with lists, but then you have to constantly create and maintain lists which seems like a lot more work than tweaking some ratings by holding and sliding an icon.