I accidentally made, like, 6 accounts, each on a different instance when first joining Lemmy because I didn't understand what federation in the field of decentralization meant LOL. Since I learned, I just kept them and have since rotated through them, partly for an illusory sense of slightly added privacy, but mostly to try to mitigate the blow of the loss of any one account in case its instance goes kaput for any reason. I guess it also gives the added benefit of Lemmy appearing more active lol (but I never comment on my own posts nor comments; that'd be wild).

Basically, if someone's response to me was interesting and I wanted to reference it later, a unified inbox would solve the problem of having to recall which account was involved.