While installing a 3rd party keyboard application is always a way to improve typing experience on your HTC device, you can still improve keyboard accuracy on the default Sense Keyboard on the HTC One M8, by doing as follows:
1. Open Settings application and go to Language & Keyboard menu
2. Open HTC Sense Input.
3. Touch Advanced and go to Calibration tool.
4. Now you are asked to type a text by tapping the circles.
5. The keyboard is now calibrated and keyboard accuracy will be improved