Mastodon and the challenges of abuse in a federated system
I don't think the problem is federation. The problem is media where participants have nothing at stake, so that abusers can't be made to pay the costs of their abuse. Changing this isn't incompatible with anonymity - for example you could require anonymous participants to post bonds in a cryptocurrency.  But e-mail spam, for example, would never have been a problem if the recipient of an e-mail could push a button and destroy $1 of the sender's money.  Getting the incentives right for a social network is undoubtedly harder, but you can't even start until people have something to lose.