In reply to Katherine M. Moss.

You could write a follow post manually in any system and simply send a webmention. I modified the Post Kinds plugin a bit to enable follow posts. Plugins or modules could be made for other systems to make it simpler though.

I think the Semantic Linkbacks plugin looks for the microformat u-follow-of on follow posts to automatically display them as a "follow", otherwise you can use the comment UI in WordPress to edit a response and change the type manually, which is what I did in Chaitanya's case.

I also manually created a Followers page to collect the "follow" mentions.