The LED's themselves wouldn't be replaced by the technician. It would be something bigger like a keyboard assembly. There are a lot of circuits and components inside involved that make your keyboard light up and a lot of things that can go wrong.
What would "I" consider as abuse/accidental damage?
If your outer cases are flush and lined up and don't have any large dents I can't see you dropping your computer to the point of it affecting internal hardware. If your keyboard or anything else inside isn't sticky or smells like yesterdays coffee, I can assume you didn't spill anything on it. If something stops working and you didn't do anything to your computer to make it stop working, it's covered.