As you yourself do in the last sentence of your text, I would rather use "interest" instead of "trust". #federation then becomes less this idealized way of enabling and fostering conversations that derives its "intimacy" from some mutual agreements. Rather, federation is a technical means to distribute interest. And as we can often observe, interest isn't the same as trust. The latter *builds over time* (and isn't there at the beginning), while the former can be intensive but also rather shortlived. Otherwise, every "un-following" would be a breakdown in trust, which I don't find to be case. That doesn't hinder, OTOH, that people who already trust each other will find federation to be good way of displaying it.