Yeah, actually I have noticed that. Mine was small this morning and then I had taken a screenshot and the phone froze and rebooted and when it came back up it was the med again and then later on it went back to smaller.
I thought I was seeing things as I was having the same thing going on. I just switched to Go SMS app. Lets me choose the max MMS size and keep original resolution which was why I wanted to switch in the first place.
There are several threads about people having problems with the SMS app randomly changing text size. However remember that just posting about it here isn't going to fix anything. We all have to make sure to contact HTC so they know it is a problem affecting a lot of people and get it fixed.
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