I used the conventional virtual keyboard. Tested also by Swype virtual keyboard.
STEPS LEADING TO THE PROBLEM:
Start e.g. website touch.facebook.com* Nokia Browser. Type some content in an input field. Tap in the middle of the text and remove some characters by backspace. You may also type more characters in the middle.
After committing the text it should look like the one in input field.
Some characters are undeleted and/or missing.
FREQUENCY OF OCCURRENCE:
*) Check in seems to work better when using this website compared to m.facebook.com