Lemmy 0.18.1 era, behaviors of Lemmy regarding data, comments and such - nostupidquestions

If the person who creates a post deletes it, how does that impact the comments that other users have made on that post? Can a user still find their personal comments on their user profile? Can you still find saved comments and posts from a deleted post?

What if it is an entire Lemmy instance that goes offline (shut down). Are postings removed? Comments? Profiles?