Soap being giggly when he's happy is a hc very, oh so dear to me.
But he also seems to be the type to giggle when he's about to cry/nervous.
I don't know the image of him talking to Ghost after maybe a more dangerous mission, starting to giggle because Ghost probably said something funny and then him just suddenly dissolving into tears while giggling. Little laughs that turn into a sob. Because he just got hit by the grief of what they do for a leaving and maybe he could've lost Ghost. Simon being hit hard with whiplash by Soap's reaction and feeling very very worried and heartbroken.