The following code compiles correctly in MD (produces a warning), but throws an internal compiler error instead in the editor:

public class StartException : MonoBehaviour {

private NavMeshAgent agent;

IEnumerator Start ()
{
try
{
}
catch(Exception e)
{
}

yield return new WaitForEndOfFrame();
}
}

Internal compiler error. See the console log for more information. output was:Assets/AgentPaused/StartException.cs(15,33): warning CS0168: The variable `e' is declared but never used.