Flip text animation right to left

Can you share the expression you use so we can see how you should flip the text, anyway, a small info here, you can't flip the animation on multi-lines text so whatever solution you get you should use one line at a time to get the animation from right to left

My first suggestion is to select the layer that contains the text, press the 'u' key twice to reveal all modified properties and figure out how the animation is driven. It should them be a fairly. simple matter to make the changes. You may also have to open your preferences and change the text properties. If the 'u' key does not work please check the keyboard shortcuts to find out which key reveals the modified properties of a layer. It is probably the same key that reveals keyframes.