"I hope you can find peace, strength and understanding with your great loss," another, from Jerry, read. "It was a miracle That You survived. Your life was spared for a reason. All the best from Canada!"
Many of them spoke directly to the boy.
"So many of us have heavy hearts from your immense loss and lifted spirits given your remarkable survival," Peter wrote.
Some talked about how his family will never be "completely gone" and how their "unconditional love" will endure.
Many people said they are praying for Ruben's recovery and his future.
"I don't know what words I could possibly say that would comfort you in this time of sorrow other than to let you know that I will be praying for you," Carol of Louisiana wrote. "I am very sorry for your loss."
And then there were tales from other people who said they also suffered a great loss.
"When I was 5 years old, I experienced a loss so great I never thought or imagined life beyond it," Brenda Vilakazi of Johannesburg wrote. "Now I am 35 years old, married with three beautiful children.
"Treasure your trip with your family. Keep the good memories alive. Happiness is all around you always. You don't need to look deep to experience it. Be at peace with all and all will be at peace with you."
Ruben was scheduled to return home after doctors operated on him and he stabilized.
"The situation is stable," orthopedic specialist Sadig Bendala told the Associated Press. "He's OK. He's not getting any worse. He's progressing quite well."
The doctor said many factors could have played a role in his survival, including where he was seated in the plane.
"It's something from God, that he wanted him to live longer," Bendala said.
Meanwhile, Dutch forensics teams will start work with Libyan officials to identify the bodies, a task that could take at least a week, depending on the condition of the bodies, Ed Kronenburg, a senior official with the Dutch Foreign Ministry, told the Associated Press.
The flight-data recorder and the cockpit-voice recorder -– the so-called black boxes -– were both immediately recovered from the crash site. Libya is being assisted with investigators from the Netherlands, South Africa, France and the United States' National Transportation Safety Board.
Kronenburg expressed some concern about the initial security of the crash site.
"We had the impression," he said, "that anyone could have walked over the site."
ABC News' Christine Brouwer contributed to this story.