See more at the announce forum.
I've previously heard reports of D code being called from C# not working right and there was another report of D code being called from Java not working right on the forum this week. See: https://email@example.com
Ali diagnosed it to a thread the Java runtime created without notifying the D runtime. With a write barrier, it'd be possible to obviate the need to notify the D runtime entirely; it would be done lazily at the write barrier boundary. This would probably help these cases too.