It's an account based system and you use their LN node to make outbound payments. The Spark service operators know your payment history, balances, and everyone you paid to. LN's onion routing makes is very difficult to tell who paid you though.

Spark can see all the transactions but like anything on lightning, they can't see who the senders are. So overall I would say privacy is quite bad, not good for privacy. But for public zaps, it's very good

nostr:nprofile1qys8wumn8ghj7mn0wd68ytn9d9h82mny0fmkzmn6d9njuumsv93k2tcpz4mhxue69uhkummnw3ezummcw3ezuer9wchsqgz9x4235sp8rvze4wftw8n6kl58qqrp5tv3krfq7vf7lqhs2t4ss5z99d3e to add to the replies, a cashu style mint blinds the amounts from its own operator with chaumian signatures, where spark's operator...