Nikolai expresses a humorous sentiment about friendship when he jokingly thanks someone for preventing him from lying about having diarrhea. He implies that if he were to lie, it would be an even worse scenario, indicating great trust in the person he is addressing.
This exchange illustrates the deep bond between friends, where even uncomfortable topics like illness can be discussed candidly. The playful banter about going to extremes for a friend highlights the loyalty and dedication prevalent in close relationships.