I understood the question wasn't whether SNI is useless, but whether its primary goal of making it difficult to track website connections is being at least partially subverted by IPv6.

>- Discourage users visiting via the IP Address, adding that to favorites, sharing it, etc. Making it difficult/impossible to migrate

That's not a reason to reject. That's a reason to issue a redirect. No regular user that would make the mistake of bookmarking an IP instead of a domain is going to know how to use an IP to get there in the first place.

>- Make it harder for databases to associate that IP Address with your site (for user privacy).

You're misunderstanding how these crawlers work. They don't just walk all IP addresses because that's a good way to get an abuse letter and because if there is no redirect to a domain they don't get the domain. These crawlers just follow links like any other and log the IPs they resolve to. The only way this helps user privacy is if there are no links to your site anywhere on the internet.

>No regular user that would make the mistake of bookmarking an IP instead of a domain is going to know how to use an IP to get there in the first place. System admins probably have caught up to this now, but a decade back I remember non-techy people doing just that. Turns out their sysadmins had blocked some social networks and people found out that you can still access the site using an IP address of their servers. The IP addresses themselves were spread across the office and many people ended up with bookmarked IP addresses. So yes, it could and has happened.