With the v0.42 release, Little Facebook Editor can cross-post to both WordPress and Facebook simultaneously, and when a post changes, both sites are updated.
As with previous versions, this is a demo app, not meant for production use by large numbers of people. The new WordPress functionality requires a server, and that means it can get overloaded.
Because there's a server involved, your WordPress credentials flow through the server, but we do not retain a copy of them. I'd much prefer if this could work without a server at all.
Use the app as before to post to Facebook.
If you want to post to WordPress, choose Settings from the system menu at the right edge of the menubar. The first and only panel in the Settings dialog is where you set your WordPress prefs.
Most of it is self-explanatory, the one potentially tricky part is the URL of your WordPress blog. This must be the address of the home page of the site. The server will look at the source of the page to discover the address of the XML-RPC endpoint for updating the blog. Best way to get this URL is to go to the home page, and copy the URL from the browser's address bar.
Click the New button to start a new post. Enter some text, and click Save. You should see a status message saying that it posted to Facebook and then to WordPress. After it's done if it works, next to the Go button there will be a WordPress icon. If you click it, it will take you to the post on the WordPress site.
Facebook posts (at this time) don't have titles, but WordPress posts do.
When sending to WordPress, we take the first line of the post and call it the title.
Make a change, click the Update button.
The changes should go to both Facebook and WordPress.
If you have questions please post a comment below. Remember this is a demo app, so feature suggestions probably aren't on-topic. I just want to help get the WordPress community working on this and provide an example for others.