I wanted to add that in contemporary use of cutting with swords in my own hands shows some blades much better cutters than others. On a scale of 1 to 10, I'm afraid I can't put any of the French mle 1822 variations of "typical" civil war cavalry sword as terrific and devastating slicers. Maybe more so with the momentum of a horse behind the wielder. Edge alignment more or less critical to be effective through any type of covering on the skin. Yes, I have cut with some antiques here in hand and even with a decent sword edge, it is somewhat a chore to develop the knack of good edge alignment. Yes, sharps that have appeared to have been ground that way from the start.
My back has seriously limited my cutting of the past couple of years but did manage a feeble few cuts against a rolled and wet mat last fall, one cut pretty much through (less one layer) that day but others mere hacks compared to other playful cutting swords I have. With that reproduction infantry type (fairly straight) with a 32" blade and my edge, I know it will cut quite well if I do my part but pretty horrible otherwise. Lots of draw in that to make it slice well.
How often the perfect cuts of history might have been made seem in the minority, while still noted. Uniforms themselves seem to have lent some protection. IIRC, it was a thought from Scottish broadsword play (McBane?) that mentions wetting a cloth to place under one's hat to lessen a blow/cut.
Hydrostatic armour?
mebbe, I dunno.
I will defer to accounts of European actions and cutting remarks. It does seem that there was still use of sharps through the 19th century (my 1854 dragon has an edge and is a straight sword). Another related somewhere that the French mle 1822 cavalry trooper sabre was not exactly loved by many that carried it but it was a defacto promise of issue for quite a few decades (and still worn ceremoniously).
Cheers
GC, ad hoc hack