I am a contributor to the Webmention plugin and the one who opened the ticket about the addition of Webmention to Core. A major rewrite of the plugin using the WordPress API infrastructure is in beta and will soon go out to the public.

A companion update to the Semantic Linkbacks plugin, which handles the microformats parsing functionality mentioned above, is also in the works.

There have been questions about what Webmentions would look like in Core that I would love to have conversations about if there was enough interest. I would invite anyone interested to comment on the Trac Ticket, try the plugins, give feedback on their development. That is how things move forward.