He totally would text in all caps.
I had to share this, cos it's been making me laugh for the last hour. XD
http://theavengersshouldnttext.tumblr.com/post/15550210664/thor-dear-angry-green-one-i-have-discovered
No spoilers for the movie, so don't worry! :D (Edit: Although there be spoilers in the comments, beware!)