Here is a trick which will help you post blank comments on Facebook.
- Proceed to desired comment field.
- Turn On Numeric keypad on the right of keyboard.
- Hold down Alt key and enter 0173.
- Use Numeric keypad not the row of numbers.
- Press Enter after releasing Alt key.
- A blank comment will be posted at the target comment field.
Note: The same trick can be used for blank Status and Posts in Facebook.