There should be an option to automatically hide the keyboard. When I open a message thread I all the screen space to be used to display past messages. This provides maximum context for understanding what was said in the last message. I always want to see this. The keyboard takes up half the screen and greatly reduces the context. It's a pain to always need to manually close the keyboard. I read 3X as much as I write. If I want to reply, I just click on the reply box and the keyboard automatically appears. This option should apply whenever you open an existing thread - either from the thread list or from a notification.