Well, today, I stumbled across how to disable the XT9 text autocompletion on my Dash.
- Go into messaging, and create a new text message.
- Hold down the alt key and press the space bar.
- A tiny menu will pop up: XT9 English, ABC, Language >, and About XT9.
- Select ABC.
- Now type. You'll notice that the auto-complete area no longer appears!