Hey folks! Just realized something that makes Lemmy different from Reddit. Because of the federation, your votes are not technically anonymous on Lemmy. At least, I think.
Although there’s no UI to look at a user’s voting history yet, one could conceivably be built by an instance. Perhaps coincidentally, I hear there’s instances out there populated by mostly bots?
No, hashing passwords is a different case because you know what the user is so you can use a unique salt. The password itself is also high entropy. For this use cause you can have at best per-post salt.
Think about it. The task that you are asking for is to quickly check if a user has voted for a post to prevent duplicates. So literally the operation you want is the same as you are trying to prevent. If you can enumerate users then you an by definition check if they have voted for a post.