My favorite 'in-universe' lore fact is probably the existence of Syndicate member Eolande Quiveron. She appeared in 1.0 and not in 2.0, with it generally being implied that she died after the Calamity, presumed assassinated, with her Syndicate seat being taken up by Godbert Manderville. The only place she appears in the live game is as a randomly spawning enemy in Palace of the Dead, where she doesn't even get named.
She's also a Duskwight, making her one of the very few main-story Duskwight characters. In fact, she's one of only two or three depending on if you count Ysayle (ancillary fun fact: while Ysayle has a Duskwight model, the Duskwight/Wildwood split happened after Ishgard closed its gates, so she and all Duskwight-looking Ishgardians aren't actually Duskwight). And the other one is Mother Miounne.
My favorite 'out of universe' lore fact, though, I mentioned when I made a recent video on FFXIV's political environment: 'satrap' is an actual title used for a provincial ruler in a number of empires that stems from the first Persian empire. Which, given who FFXIV's satrap is, is really clever.
They didn't give the satrap a title of a lesser ruler just because it sounded cool; they gave the Satrap a title of a lesser ruler because he is one and is hiding that.