pack ice princess

he’s the worst kind of sorry

He still has food on his plate, but his cutlery is placed together to indicate that he has finished. This could mean any number of things.

In the dinner scene, Crozier is the only one who has completely cleared his plate, which means he probably has not spoken a word the whole dinner and has been eating in order to prevent himself from saying something rude. Notably, as soon as he does finish eating, he takes a drink and then immediately makes the Bird Shit Island comment (first spoken word at dinner?)

Also the fact that JFJ has fully turned his whole body to the side and propped his leg up to chit-chat is so funny to me. Like OP said: His silverware is also placed in a position to signal that he is finished with his meal, even though he’s left half of it untouched.  I’m a bit surprised that his plate hasn’t been cleared away by a steward to be quite honest. Though, as OP noted, he might have done this because he's failing at etiquette. AND since he is incredibly good at his job, Jopson would have picked up on this and would not want to embarrass the gentleman by drawing attention to his blunder. Though notably, Crozier places his utensils in the finished position on his plate and it is not cleared away either.

JFJ is also fiddling with his fucking napkin ring, which is a BIG no-no.

Another interesting tidbit is that Crozier, Sir John, Little, Irving, and Hodgson are all dining according to Continental Etiquette, which entails keeping your knife in right hand while you eat, with your fork tines down in your left hand. When you take a break or a drink, you place both utensils down in essentially the same position on the plate (as OP noted above). Dining like this would have been typical for a well bred Englishmen at the time. Here's Edward looking so handsome with his proper Continental Etiquette:

The exception at the table are McDonald and Helpman (idk how JFJ might have been eating before, though)...

McDonald is eating in line with American Etiquette. This entails holding your fork with tines UP in your right hand with your knife placed on the plate at a forty five degree angle in the upper right. When you need to cut something, you transfer your fork to your LEFT HAND and hold it with the TINES DOWN and then you pick up your knife to make the cut (essentially assuming the same position as Continental style). When you are done cutting, you place the knife down on the plate at a 45 degree angle in the upper right, with the cutting side facing in (MacDonald fails to do this, and leaves his knife facing OUT!).

idk what the hell Helpman is doing -- He's holding his knife according to Continental style, but then he has his fork in his left hand with the tines up similar to American style. This would be INCORRECT in both dining styles, but he could also be left handed, but he should still be placing his knife down instead of pushing his food around with it. He also has his napkin UNFOLDED under his right wrist, which you should never do until your finished with your meal (and it should go back on the left side).

I'm unsure if these two characters are dining improperly like this as some sort of indicator that they are both of a lower class than the other officers at the table -- Mr. Helpman being only a petty officer, and McDonald being Scottish (though educated and relatively well bred?). I was unable to find anything substantial on Scottish or Irish or Welsh dining conventions online....

Which brings me to ANOTHER point.

In my experience, these rules are rarely, if ever, written down, but rather taught by parents, tutors, or at finishing school. adherence to these tiny rules are a a form of in-group signaling, to indicate to one another that you are not only wealthy and well educated, but also have GOOD BREEDING, as people who are in possession of "new money" or who trend towards the middle class (perhaps like Helpman and McDonald) might be unaware of some or all of these rules. This is why I find it significant that the captains and lieutenants, are all dining according to convention but JFJ, Helpman, and McDonald are floundering a bit.

I’m curious if all of this was a conscious decision by the actors/showrunners or if it’s just naturally how the actors ate. 

Also, I enjoy taking a look at the scene with the ships boys & Hickey from directly before, because they’re all eating with spoons in their right hand, and especially David Young is holding his spoon very poorly.  The juxtaposition demonstrates very clearly the class difference between the two rooms, not only in how they hold their utensils and prop their elbows on the table and speak with their mouth full, but also in that they are given only a metal bowl and a spoon.

The dashing Commander Le Vesconte wore a peculiar prosthetic on his face, made of silver and crafted by the finest surgeons in London, in place of what the frostbite had claimed of his nose during Sir John Franklin's expedition. On his missing leg, there were far fewer commentators.

not on my ship

at your service