More “portable” and secure identities would have been a good feature. The client could have handled most of the crypto required for signing and validating content. As it stands now, the instance Admin has complete control over your identity. Portable communities would follow that easily.
Most of the syncing issues are actually between the large instances or instances that having performance issues.
You mean blocked instances right? AFAIK an instances “blocked users” is not published in aggregate. You’d have to comb through the modlog.