What do the icons next to a soldier's rank icon mean?
In combat, your selected soldier's rank is displayed as an icon at the bottom left corner of the screen. Sometimes a yellow star or a white cross will appear on top of it. What do these icons signify? Are there any others?
The yellow star indicates the squad leader, typically the highest ranking or most seasoned soldier in the squad. There's not a lot of in-game indications about what this means, but from experience I believe there's a higher chance of your squad members panicking if this person goes down.
The white cross/plus indicates that the squad member is up for promotion... assuming they survive the mission