Navigating to previous chat messages is glitched on iOS and Android

Affects 1.20.60+ on Android and iOS

When using the keyboard's arrow keys to navigate to previous messages, you can't move the text caret past the first character. If you start typing, the text will come up but the caret will be in the wrong position. You also can't delete any of the previously sent text.

This is a major problem (especially for mapmakers), and makes it harder than it already is with existing recently introduced chat bugs.