Gantry 4 included integrated, built-in support for right-to-left (RTL) content. This support was apparent throughout the administrator including a toggle enabling you to turn its RTL functionality on and off.
Gantry 5 also supports RTL, but it takes advantage of the fact that virtually all modern browsers support it inherently. This enables you to use RTL in your site's content without any administrative toggles needing to be switched by the developer.
In a sense, we've cleared the way to enable you to create RTL content and have worked hard to ensure that the framework will not interfere with you doing so. How this content is rendered depends on the browser, and not all browsers handle RTL the same way.