MSC: Comment should move according to linked entity

When a message that contains a comment is moved, at the moment the comment does not move together with the message. It remains at the same absolute location

This is not right. The comment should be moving together with the message (y-coordinate)

That causes an issue when loading a generated MSC. Sometimes messages are automatically pushed down when you render the scene, but the associated comments are not. The resuling diagram is messy