Any post and community could be accessed through a theoretically limitless amount of instances, which also means a theoretically limitless amount of URLs.
Will this hinder Lemmy from ever coming into the mainstream? If I type any topic in Google, I will get a reddit thread that deals with that. Can something like that ever happen for Lemmy?
Currently it appears that a non-logged-in user (try an incognito window!) will only see posts on a particular server’s local communities. So a search engine bot crawling multiple Lemmy servers will only see duplicates if they’ve been explicitly crossposted.
No, you can definitely browse “all” while logged out. It just defaults to local.