[WorldMaker]

The easiest way to merge multiple toots originating from the same person (through multiple federated accounts) is not to need to merge them in the first place.

Admittedly, the current intent is that you (person) keep individual toots to specific instances and don't "cross-post", but there may be all sorts of reasons to need to cross-post across identities but try to avoid spamming federated friends.

Email doesn't need to solve the problem because there isn't a "public feed" to try to hit. The issue here is that the individual feeds in an instance are always going to be complicated game to play to get attention and the next steps are going to be instance-feed-optimization (IFO?) techniques including mass cross-posts, whether the Mastodon community wants to see that or not. (Just as advertisers still care to optimize how they show up on the Twitter public feed...)

Portable cross-instance identities are a possible way to mitigate some of the worst of that. My pessimism/cynicism thinks that maybe Mastodon instances shouldn't have instance and federated feeds publically visible. If I were to run my own instance, that would be the first things I'd disable.