Messaging keeps drafts after you have edited and used them Running a Galaxy Nexus on Jelly Bean 4.1.2. Stock, with stock messaging app.

I find that when I create a draft message because I've accidentally hit home instead of space, when reloading the messaging app, editing the draft and sending it, it keeps the original draft in the 'Type message' input box.

Why doesn't it get rid of it, when the draft has been used and is therefore no longer needed?

Is there a setting somewhere to control this? (I couldn't see one.)
I just figured out how to get rid of that. Tap on the message like you are going to add to the message. Click the Delete button. Then you should see text in the background that says "Enter Message." Click the back button on the phone. That should take care of it.