Anyone on a federated server can see this post. I'm on my own personal server for example. There's no local content whatsoever. I'm getting all content through federation which basically means that all the servers are agreeing to talk to each other and share content. It's like a group chat but for websites.
Great question. Without knowing the answer for sure, no. I don't think the comment lives on my server but rather the server that the community belongs too.