As part of its steady march toward version 1.0, Writefreely is gradually expanding ActivityPub support. For now, I can push full posts out to federated platforms, like Pleroma and Mastodon, but I can't pull in responses to those posts. The planned solution (as I understand it) is Remark.as, not yet in release. The interim solution, it seems, is to use Writefreely's integration of ActivityPub mentions to alert a Mastodon-native account whenever a post gets a reply. So for the time being, if you reply to one of my posts, you should expect my response to come from my account @firstname.lastname@example.org.