It’s doesn’t get inherited, so it would need to be applied to every element in a cooked post. Also, Internet Explorer doesn’t support it. If we’re not concerned about supporting IE, there are places in the code that it would be useful (titles, category descriptions, etc.), but it’s easy enough to add a helper function that sets the direction of those elements based on their text content.
It automatically applies the correct direction to text in the preview window, cooked posts, titles etc. It sets the direction of text fields based on the text that is entered. It doesn’t automatically set the direction of the composer’s textarea. To make it easier to type, you can switch the direction of the textarea by clicking a button. Changing the textarea’s direction doesn’t affect its final output. It will be formatted correctly regardless of the direction the textarea is set to.
Facebook’s editor handles text direction very well. They can do this because their editor is using contenteditable. This lets them set the text direction on individual elements in the editor. It’s possible to get behaviour similar to this by adding the attribute dir="auto"to the composer’s textarea, but doing that has some strange side effects.