A Nahhamu Devar Torah from Rabbi DINDŠ
The question is, what's מבשרת ציון scared of, such that in the הפטרה of שבת נחמו she needs to be encouraged by the קול not to fear when she goes up onto the mountains to announce Redemption to a dry-grass world?
To answer, look back at the parasha, ואתחנן, in which Moshe begs God to let him into the Promised Land, but instead gets told to go up onto a nearby mountain to get a nice view of Cana‘an... because he'll never see it close up.
Maybe the מבשרת ציון is scared that if she goes up the mountain with her message of messianic peace and wonder, she'll never make it all the way there, like Moshe Rabeinu. But the prophecy continues with descriptions of God's transcendent greatness — measuring out earth and heaven, naming every single star beyond — to reassure her that this future redemption is being driven by a Force that knows what it's doing.
At first I thought it could mean that when redemption is enacted by God directly, every individual (like the stars) will not be lost, unlike with Moshe who was a human being dealing with the people on God's behalf. But we don't always think of the future redemption as Divine handwaving and handholding... so what would that mean for a process of slow human process towards the perfection that God has pointed us towards? Maybe it's an end to fear and worry. Maybe מבשרת ציון will never make it to ציון herself, but she should not give up hope. She's just a little piece in a big play, and everyone does their part to water the dry grass and weary minds so that they will sprout hopeful futures.