Juhana already knows. (See Borogove: Online editor for Vorple, Inform, Hugo and Dialog - #54 by Juhana).
The way Monaco (the editor used by Borogove) misbehaves with Android depends on which keyboard app you use. I’ve seen text duplication, text being inserted on the wrong line, and the backspace not working. I suspect Monaco doesn’t listen to the web input method events.