An error message now notifies users when they try:
Update Unavailable with This Apple ID
This update is not available for this Apple ID either because it was bought by a different user or the item was refunded and cancelled.
While Apple has never had an automatic way to get refunds for apps, Apple does allow users to "Report a Problem" on their purchases and options include ways to get a refund.
In the past, customers were allowed to continue updating and reinstalling apps even if they were given a refund on the price of the app. This new functionality has also been extended to the Mac App Store.