Yes I just tested it myself. Nice, no need for browser plugins on Android.

The above event is kind-1, not nip-84/kind-9802. I am confused.

I don't understand how else to say this... I'll try again. Amethyst supports using your finger to highlight text from a web page and sharing that text and web page URL to Amethyst. The event that is shared is a kind:1 event and not a kind:9802 event. All Vitor needs to do is change the event kind and spec for this event. Alternatively he could just add a second Amethyst share intent for for this specific highlight kind. Amethyst and Android have the capability, but it's currently not being utilized. There should not be a dev headache like you said, because it's technically being done right now with a different event kind!