Old block has been removed in this version, instead please add the dependency of these 2 blocks and the client action into your target module where you need to do the comparison and highlighting.

Take dependency of these blocks and action.

Drop these 2 blocks into your screen.

On click of Diff button action, add the client action like below.

Now pass the above assigned result text output as the input parameter for EscapeHtml block,

Thats it. publish and test it.

I have included DEMO also. please download and check it for more detailed information or if you have any doubts regarding the implementation.