I agree with everything else and think "managing group messages" has other issues. For example, it's nice that I can duck out of an iMessage group, but can't duck out of a text message group or email chain.

mailing lists

> no shared history support

Your own client or provider can store history. you also don't own someone else's history - a good feature imo.

> no consistency about how previous replies are referred to (e.g. different quoting styles)

A preference for individuals to decide.

> no real identity support

What's a "real" identity? my email address is my identity.

Also, wouldn't encryption fix this problem? I don't understand how it might be implemented in the real world, but if you encrypt with your private key, then their public key the message should be safe in transit, and at rest (unless they leave it decrypted on disk)