You can see posts and you can see replies. You won't by default see posts and replies that you didn't subscribe to, or that aren't addressed to you.

If your preferred experience of social media is sitewide trending stories, or searching for topics, single-person Mastodon servers aren't a good fit for you. If, like Julia Evans, you have both a large audience and a network of people you talk to on the regular, it's probably pretty OK.

If Mastodon succeeds (I'm rooting for it), I expect single-person servers, delivered by hosting providers like Masto.host (but a generation or two away, like Blogger vs. the first generation of blog software) to be the normal way people use it.