I saw this in an Android phone (Honor 8) while creating a new forum discussion as teacher. When the keyboard is open the editor is reduced to a single line, so it can be a bit hard to use. This might be happening because the page has several options below the editor (pin, subscribe, etc.). IMO we should set a minimum height for the editor so it doesn't become unusable.

I noticed another error in the same place. If the editor is disabled and I focus the editor so the keyboard is opened, the button to view the editor disappears. If I close the keyboard then it appears again. This doesn't happen if the editor is enabled.