I have been using the xmlrpc interface to post to my blog. Since the metaWeblog API does not allow me to specify if I want to be notified of comments, and there is not a default setting in the core of pLog, I wrote this plugin.
This plugin listen to the EVENT_POST_POST_ADD event, and adds an Article Notification to all new articles that do not already have notifications enabled.
You can download the plugin here.
For use in the xmlrpc api, the patch described in this bug is required, as well as pLog 1.0 pLog 1.0 is required.
Update: The latest version of pLog has the patch previously described.