Can you explain why you'd use a label over a hashtag? My thinking is, events should mostly be tagged by others anyway, which would be a label according to NIP-32, if I'm not mistaken. If so, this makes sense to me. I also like the idea of tying NIP-51 pin lists to action, like if I pin something, it means I'm keeping a copy of it/requesting that relays do the same. These feel like the most "meaningful" interactions to encourage, outside comments/zaps, at least that's guiding my approach.