Why doesn't posting rich text format work?
The rich text format will only work when publishing posts to Facebook, Instagram, WordPress and other blogging sites (such as Tumblr).
If the rich text editor doesn’t appear in your Compose box for any of these social sites, you can turn rich text editing manually on by going to your Settings > Preferences > Publishing Preferences > Rich text editor.
You can set your rich text editor to come up in your Compose box to:
Automatic - the rich text editor should appear for only the above sites
Always on - the rich text editor will appear in your Compose box all the time; choose this if the rich text editor didn’t appear for any of the sites mentioned above
Always off - the rich text editor should never appear at all
With the rich text editor option "Always on", rich text editing will always display in your Compose box even for the profiles not supporting rich text editing.