The issue is if invoke any command like getHTML or setFocus on the control the key event is not happening any more. I was able to reproduce this issue on the above mentioned link.
The Following steps will reproduce the Issue i am talking about.
1. Click on attach Event(on keypress) button
2. Now type the text in the Rich Text Editor and onkeypress event is fired
3. Click on getHtml or setFocus Button.
4. Now enter the text again in the Rich Text Control and onkeypress event is not fired
I was able to get the event fire by clicking inside Rich Text Editor first and then type the text then the event fires every time.
Please let me know the fix or workaround for this.