RonParker noted about the carriage return gesture:

  1. Make the gesture the exact corner of a square
  2. Pause a half-a-micro-second in the corner of the square
  3. The inside corner of the square should be just TOUCHING the right and bottom edges of the last word or character where you want to insert the line break, NOT on top of that character nor floating in the space after or below it. This really improves the accuracy, helping your Newton see the gesture as a "gesture" instead of the insertion of a "J".

VictorRehorst noted about the carriage return gesture:

  1. Try starting the stroke on the lower half of the line
  2. Bring the pen down to below the bottom edge of the line
  3. Pause slightly without lifting the pen
  4. Then bring the pen left underneath the line.

That's what works for me. If you angle the second part of the stroke up towards the line of text, you'll get a J.