He probably means using the ¨ modifier on a non-native keyboard. I do that daily after I picked up the habit of using Danish keyboards. For the record, it's a

He probably means using the ¨ modifier on a non-native keyboard. I do that daily after I picked up the habit of using Danish keyboards. For the record, it's a habit you get used to rather fast; nowadays I use the ¨ modifier for ä and ö even when I'm using a Finnish keyboard.