Add integration of Text-To-Speech to articles, for example with Natural Reader extension or Read Aloud extension.

They have many awesome voices and in many languages.

Add a button to each article's page to speak it, and to start speaking from the beginning of the word clicked on, and not its middle where the mouse pointerwas.

This spreads awareness to TTS in the world and on KhanAcademy and people start learning and comprehending faster as they listen with ears and read in eyes at the exact same moment, simultaneously.

Speech is even more advanced in humans than reading because it preceded it evolutionarily. So eyes and ears at the same exact time duration would make studying easier and more fun and one can pause, return to another point with a mouse click.

Same about KhanAcademy mobile app, make it be able to speak the text while seeing it too.