Nope, atm the chest is not reachable. It's like the issue with our cute assassin who's supposedly somewhere in Aleroth.
The problem is that the game replays the cutscene with the dragon all the time you're too close to the edge. So there is definitely no way to reach the chest
To the harbor: I think you know that you can enter the main hall with the docks. The fortress behind this hall is afaik not reachable, since you cannot open the gate by any means
So both issues are dead-ends.
My speculation is that these phenomenons are remnants of content that was not implemented into the final game.