Tag keys starting with 'aws:' are reserved for internal use (Service: AmazonEC2; Status Code: 400; Error Code: InvalidParameterValue; Request ID: 670e59a1-a1ac-4044-8d27-9caf9ef1218e)
In terms of this, terraforming imports them, than plan shows a change, apply fails silently (looks good) then plan still shows the tags need to be added.
Using these via the CLI/SDK will error:
Tag keys starting with 'aws:' are reserved for internal use (Service: AmazonEC2; Status Code: 400; Error Code: InvalidParameterValue; Request ID: 670e59a1-a1ac-4044-8d27-9caf9ef1218e)