This probably has been asked a million times, so apologies in advanced. But can we log into other instances with our login here for example if I went to lemmy.world and logged in with Designate6361@lemmy.ml should this work? Or do I just need to make an account on their instance as well ? Already know how to browse and comment on other instances but this was interesting me to know if it could be done.
You can’t, but there’s no need. You can read posts to communities on other Lemmy servers from your account on lemmy.ml. You can subscribe to those communities and comment on posts there as well. There’s no need to have an account on each server. It’s like email. You don’t need an email address on each server to send/receive email. There may be a reason to have another account - maybe you get really involved in a community on that server and that server feels more like home. But, no, there is no protocol for cross-authentication.