Okay I'm trying to analyze the themes of the Remarried Empress (a difficult task since a lot of Manhwas I read are fantasy romance, a genre that will neglect a conflict or meaningful obstacles for two bland little leads)
And the main one I'm finding is that the obstacles and course of the story are affected heavily by historical precedent. A lot of screen time is given to talking about ancestors, previous mistresses, previous emperors. When sovieshu crumples up the wedding invitation from Navier and Heinley, his advisors first concern is that future generations will realize that Sovieshu was angered at it. Heinley's entire clan is pretty much wiped out and recorded deragoatorily in history (a bit tangential to the theme I stated but perhaps it would be better to expand it to be the influence of history)
Navier, as our protagonist, has the most clear understanding of these historical precedents and is very aware of how she must conduct herself. She's very strategic throughout the story with using these precedents and deciding when to break them.
Perhaps a foil is Krista, the former queen of the Western Kingdom. She is stated to be very similar to Navier, they are described, dressed, and speak in similar formal ways. However Krista isn't smart about when to retreat, (something that sovieshu explicitly judges Rashta for during her child's banquet scene with the decorative sword,) she's doesn't follow tradition (and because it's manhwa rules, she's punished for laying eyes on Navier's man). She doesn't follow historic precedent of retiring to the (??? I forget it's name) estate. Since I'm mainly consuming this through webtoons, it's a little hard to tell what statement this could make on the whole historic theme, but I'm looking forward to it.