Amongst the numerous changes in Windows Phone 8.1 is the strange movement of the comma key from the first level keyboard to the special characters, which apparently occurs when multiple keyboards are installed.
It turns out fortunately this is an easy change to reverse.
Simply go to Settings -> Keyboard –> Advanced and check Show a comma key when available.
Besides those changes Windows Phone 8.1 also has a new cursor key, now working the same as Windows 8 Metro, with the cursor being manipulated by touching the small circle below it. The new cursor is more intuitive and allows more precise selection and placement, so overall seems to be a positive move.