I don't hate Nimmel. I don't want Nimmel to die, specifically. But Mookie uses the omniscient perspective to highlight certain points. He didn't just make Nimmel disappear with no further word until he brought it up here again, but showed us how he was trapped and worried for his friends. This has the obvious intention of making us feel bad (a good writer would use it with that intention anyway). The thing is, you can't feel bad when you know they'll find a solution soon enough.
Take Game of Thrones (since it is popular now). Characters, beloved characters, die there all the time. And everyone loves the show. The reason is that the deaths of those characters makes it clear that anyone could die at any moment, so when you see a character in a difficult situation you feel dread, feel happy when they survive a scrape, and ultimately feel bad when they die. One of the points of reading a story is to feel those emotions. Especially the sad ones. But Mookie consistently cheapens those emotions, to the point that everyone here feels nothing at all. I can't feel bad for a character that will come back from certain doom a month from now.