esampson
SOC-13
My take would be that the vast majority of duels would be 'first blood' types of things. One of the reason many of the codes that governed nobles in battle evolved was so that the nobles wouldn't kill each other (or at least the odds were reduced). Thus it became acceptable to hold a defeated noble prisoner until their ransom could be paid (or they ceded control over the contested territory).Interesting. Sword duels don't actually have to be fatal either. First blood duels could be more socially acceptable than dueling to the death. Dueling scars could go in and out of fashion. . .
On the other hand some matters might be so grave that it would be understood that only mortal combat could settle the matter. This probably wouldn't be viewed as socially unacceptable as a general thing as having a dead noble is probably preferable to having planetary bombardment but in the specific it might often be viewed as socially unacceptable (one Baron refuses to retract a statement about another Baron's wife, it would quite probably be inappropriate for the second Baron to challenge the first to mortal combat).
The social prestige of dueling scars would probably vary greatly depending upon the planet/culture of the character. I mean Dulinor came from a culture where it would have been considered an insult not to be armed in the presence of the Emperor. I'm sure they would view dueling scars as badges of honor. On the other hand Imperium medical technology is probably good enough to remove nearly any scar so there would almost certainly be cultures where having such a scar would be viewed in the same light as a noble tattooing 'Badass' across their forehead (since it would essentially be almost the same thing).