But that sort of depends on one's definition of what Canon is. To me...canon is the main route I always play first. (or my most favorite romantice route in a game). So for me, the canon is Damon/MC with a long-over old romance with Alisa. So in my Damon route, I'm cool with how it is.
If in the other routes, that's different and Damon still has a thing for her, that's cool, since that isn't my canon route. Guess it comes down to the individual.