I was writing a post in a thread on my iPhone 5 iOS 6.1.4. It was a long post and I had to scroll up when my keyboard overlapped my text a few times (keep reading this is not the bug)
By memory I had to fix a typo so I think I had clicked on a different paragraph to fix the typo. I then had to go and do something and while I was gone my iPhone went to sleep.
When I came back and unlocked my phone the editor had resized and half my text was hidden and even holding my finger down and scrolling down would not bring me to the bottom of my text.
First pic showing you what happened. You can see the text is cut off. That's never happened before.
Second pic showing you I can't get to the bottom of the text.
Third pic I had clicked more options and now you can see I had more text that I could not see previously.
If I reproduce this I will give you the steps. So far I have not had this happen again trying the same scenario.