alt Hacker NewsIPv6 link local layers over Ethernet the same way Arp does. Both contain a source/dest MAC which is used for forwarding, both contain the relevant neighbor info. If anything, keeping the protocol's self-discovery messages wrapped in the protocol itself is actually cleaner layering at the cost of complexity (the extra link local signalling addresses).
It really is not. There's a whole morass with possibly overlapping "on link" networks that nobody can implement correctly on the first try.
Then there's this whole pretend "it's not broadcast but multicast" song-and-dance with ND in IPv6. In IPv4/ARP the separation is clean, and no lower protocol details leak into the IP layer.
Link-local addresses were also meant to be used for LAN-only apps. Except that it quickly turned out that you can't actually use them reliably because some interfaces (like PPP tunnels) do not _have_ MACs.
It's a mess.