![Wink ;)](./images/smilies/icon_wink.gif)
I read the silliness and playfulness as being part of his personality that he'd always had, but had ruthlessly suppressed in order to set a good example for his men and because he was half-ashamed of it. It didn't seem to fit the image of knighthood and leadership that he'd had. Once he was free of the guard and trying to find himself post-Zophar, he tried the silly mask thing and flamboyantly swashbuckling style near Takkar (breaking all the windows in the process, as I recall), probably in part from reasoning that playing it straight hadn't done much good previously and in fact had closed his mind so much that he nearly blew it with blind obedience. He went from the romanticized role as White Knight of Right to a Zorro-type, equally romanticized but unofficial.
It's actually somewhat similar to what Ronfar did earlier, I think: Ronfar probably had big idealistic dreams of being a great priest-healer in Althena's service, but his disillusionment and traumatic separation occurred earlier. So his healing became more clandestine and unofficial (everyone in Larpa knew that he was a healer; remember EB's itching grandpa?) and he went for the romanticized image of the gambler with a heart of gold. Once he had his baggage straightened out he settled down with Mauri and presumably no longer needed the image. Likewise, I'd expect Leo to become more like Laike eventually after he worked out what he really wanted to do; he was still in that process at the end of EB.
With Mauri, of course, we see what happens when that step of disillusionment doesn't occur. Of course, she didn't have much choice, being drugged. But I would hazard that the three of them, growing up together, had dreams of changing the world and all, and reinforced each other's childhood dreams. In another era, Leo would have been a Dragonmaster, and Ronfar and Mauri much-beloved high priests. Which thought makes me wonder if it bothered Leo that Ghaleon was already in the Dragonmaster role, officially. Ghaleon tells Leo that he doesn't care for the title, but this probably utterly bewildered Leo.