Like I said, different people different opinions. And it depends very much on what one is attempting to accomplish with the tank, i.e, enjoying a "community tank", or maximizing the performance of individual fish in growth, reproduction, etc. They can be together, but a number of people don't advise depending of what is desired. But it is certainly possible and from your posts I interpret you have been doing it already.
Several reasons - Depending on the type of angels, specially domestic strains, most of them prefer somewhat lower temperatures than many discus (also depending of types of discus, either wild, or domestic strains). Of course aquarium strains are more adaptable. Also, angels are often more aggressive at eating than discus, potentially outcompeting them, and have somewhat different diet requirements. If pairings take place, there can be additional competition issues.
Good luck. It sounds as if it would be a very nice tank and community.
