While that might be nice, I'm not sure how possible that is. No, I meant that when I tap on the field it would select the prefiled data (it usually appears highlighted when this feature works).
For example: The fruit field is prefiled with the word BANANNA, but I want to enter KIWI. When I tap on the fruit field the word -BANANNA- would be completely selected. Then I can just begin typing my desired word -KIWI-. Let's say I want it to remain BANANNA, then I would just hit enter.
Currently if I begin typing I would get -BANANNAKIWI-. To get just -KIWI- I have to delete -BANANNA- first.
Does that help? There are many places within OLLY where I could see this being useful.