When in a world, tapping the chat button up the top and entering the chat panel, the keyboard covers the chat box and you can not see what you are writing.

Steps to retrace:

1. Open up Minecraft.
2. Enter a world
3. Tap the chat button to the left of the options button
4. Tap the chat box below.
5. The keyboard will appear and block the view of the chat box.

Using iPad 5th generation

iOS 13.4.1

Minecraft PE