Neshuk
Spock prepares for this task, as he prepares for anything else: With purposeful intent, deliberation.
He suspects that the other members of the crew would not see the logic in this activity.
Spock is known on this ship for his efficiency, his precision, and the rapidity with which he performs his function. He is known for his logic.
Performing any task well is logical.
Performing any task well carries its own beauty.
And Spock is Vulcan: He takes pleasure in performing a task well.
There are other methods of performing this same function that are more efficient. There are others more rapid. There are others, even, that require the same precision to be done well.
But there are none as beautiful.
This note will be nothing special. It will lie on her pillow until she lifts it and reads that he has work that must be done, now, in the time before she goes to sleep.
These are ordinary words that would be expected to bring her sorrow, however mild.
Knowingly bringing sorrow to another is not logical.
He dips the pen and writes, taking pleasure in the characters unfurling rapidly, precisely, efficiently from his pen. He takes pleasure in the ink lines of his native language flowing down the page. And he takes pleasure in knowing it will bring joy to her to read his message delivered in this way.
Indeed, this task is eminently logical.