That breaks significant assumptions of the WWW. Specifically, it means that devices have different addresses when accessed by different hosts, which breaks all hyperlinks the Server may send back, unless the User Agent also sends the scope ID to the Server. However, the scope ID is meant to be meaningful only in the context of the host that originated it, so RFC6874, which introduced this concept officially in URLs, prohibits sending it.
Overall, this means that, in practice, WWW on IPv6 does not support link-local addresses. This is especially true given that none of the major browsers support them.
Overall, this means that, in practice, WWW on IPv6 does not support link-local addresses. This is especially true given that none of the major browsers support them.