Would you as Emperor want to have a sector duke taken out by a lucky shot or hit in a duel?
In duelling cultures, one typically duels only with one's social peers, so it would be most common among the more junior levels of the nobility -- where there is also a greater need to establish one's honour.
OTOH the US is an example of a nation in which duelling occupied even the most senior members of government, in the early 19th century.
... quietly ignored in the IN and IMC so long as both parties show up fit for duty the next day.
Interesting duelling factoid: in the early 19th century, the US navy lost more junior officers to duels than to enemy action.
If it's firearms, you could use a non-lethal round ....
Possibly the Imperium could have a modernized duelling culture in which non-lethal weapons took over, but this detracts from the very point of the duel, which is to establish your honour via your willingness to die over a point of honour. Welts don't cut it.
The usual practice is "first blood." That is once you score a hit and do it first, the duel is over and honor satisfied be it a punch to the nose or running someone through with a sword.
First blood is the usual practice. In fact, the reason I thought of this is that a foil is unlikely to inflict a lethal blow. This lets you risk your life over a point of honour without actually taking too much risk.
I have a hypothesis that the decline in duelling in the US beginning in the mid 19th century may have been partly a result of the Colt revolver. Smoothbore duelling pistols are woefully inaccurate; rifled revolvers much less so. Too risky.
Meanwhile, in Europe, the duelling tradition continued. One of the salient features of the European duelling culture was that it remained a fencing culture. And in the French tradition, a gentleman could decline to duel with cavalry sabres without loss of honour -- again, too risky.
BTW, as far as first blood goes ... fists were out. To strike a gentleman with your hand was the ultimate insult against honour. To suffer such a blow without challenging the offender to duel was at one time unthinkable.
Imperial traditions may vary, of course.
Dueling isn't that far removed from us. French politicians routinely dueled up until the First World War.
The duelling tradition was very strong in the US, especially in the south, before the Civil War. The oath of office for Kentucky's governorship still requires the governor to swear that he has never involved himself in a duel.
