It could be a “verified” follow if there was a zap. I’d figure that zap would still be there if you unfollowed and followed making future actions “free”.
Discussion
If the broader question is “who is likely not a bot”, maybe if a npub has sent 1 sat, 10,000 sats, or another amount we could mark as “this profile has zapped” (irregardless of follow).
Maybe does not mean much if nostr:npub1l2vyh47mk2p0qlsku7hg0vn29faehy9hy34ygaclpn66ukqp3afqutajft DVMs normaize AI agent LN payment send and receipt.