Yes, we need that for the ranking, trust graph, rewards etc.

The frontend polls your user every 5 seconds, so you should assume yes.

We could correlate logouts and login to make educated guesses. For example, if the switch from account A to account B always happens within a few seconds, it's highly likely that's your alt.

A while ago, I wrote code for account switching but the code was messy in parts where we certainly don't want to be messy (the authentication layer) so we didn't ship it. But when we release account switching, you don't have to logout anymore.

But since we didn't find a secure way to only send the cookie of the account that you switched to (since the actual cookie used for authentication is HTTP only as it should be), we could look at the request cookies since they will contain all accounts that you can switch to. So it would actually be easier then to link accounts if you use the account switching feature.

When I take another look at the code, I might find an approach that works that keeps accounts unlinked. Open for ideas on this.

No, we never store IPs on purpose but they might get stored in some rotating AWS logs but @k00b would know more about that.