I like the made up words which do convey a meaning despite nonsense. They even made this one a real word.

He is pointing out his being ostracized when nobody is paying attention to whether he is.

The sense of smell is often said to be the most closely tied to memory

This is in reference to linguistic differences which cause accents.

These faces are moving quickly, seen and then lost in a crowd (disappearing like an apparition,) and provide a pleasant relief from the environment, like petals (a positive image) on a wet black bough (which invokes a grim or forlorn image)

The author does acknowledge the evils which take place,however he points out the good things about the city.

The author here expresses regret at his choice to "keep half" of him in the world of men. He would rather not be caught up in real life and live more in a fantasy, so to speak.

holding the poem up to the light is the way of appreciating the meaning of something, but (like a slide) you can't truly appreciate it unless you "hold it up to the light"