I've read conflicting things on posting to different Lemmy instances than your home instance

I've read that it should be possible, but my experience seems to show that that is incorrect, that you need a login for every instance where you wish to make a post or comment. Could someone who knows clarify this?

If you need a login for every instance of Lemmy to participate in non-local communities, then that will, I think, be the #1 issue with Lemmy adoption, and the main reason folks bounce off.

Edit: I was trying to comment on a post on lemdro.id, but it said a login was required. If that is to be the case, most users out there won't understand an ability to see content but not participate in that content, simply due to instance logins. That was my point. If that isn't true, and I should be able to comment on other instance posts, then I've experienced a bug or something.

Edited Edit: I believe this was a result of using Liftoff, where I was able to view a community on another instance, and I was logged into the app via my own instance, but it treated my viewing the other community as if I were on that site, instead of viewing it through my instance. So this things are, I think, working as intended, and that Liftoff made the presentation of things ambiguous. Thanks for all the polite replies. Definitely makes me feel more confident that Lemmy can be a good replacement for Reddit.