I think the point is being missed here, Federation is one part of indieweb, but the biggest part is being in control. When external places decide to close shop, you lose everything, you have zero control. But if you post somewhere you control, you make the decisions.

That's why I download a copy of all the responses to my posts and serve the copies from my site. By now I'm sure there are plenty of cases of comments on my posts that are gone, but they still show up on my site because I decide to keep them there.