Thanks for your feedback!

1. Posts are reviewed and read by our human curators, manually voted.
2. You get automatic refund if you have received vote in last 6 hours, taken from time of boosting. If you did, you can always wait a bit and boost after 6 hours from the time you received your last vote from esteemapp.
3. You do get your ESTM back as refund, so you can boost again.
4. You post have no votes or has 1 vote only when you boosting, that might also cause refund.

In your case, likely scenario is 2 or 4. So if you try boosting again, it will likely work.
How would you want us to improve refund message so that it will be more informative?

To your another point, I just wanted to add this: "free speech" is that nobody can block/remove your post because it resides on blockchain.
Hope it helps, don't hesitate to reach us out on discord for real-time help or feedback!