Is listing one item in multiple categories recommended?
Do you mean in separate listings? I'm pretty sure you can only use one category per listing.
If you have more than 1 available, you could list one in one category and another in a different category.
If you only have one, that could be problematic. I vaguely remember reading a policy about having what you are listing available (at least within the processing times) and if the 1 sells, you'd have to manually remove the other listing.
Try using SEO to cover all the category bases with long tail tags, etc.
It could be problematic. Years ago I had an item listed twice so that I could show it with different listing pictures. Someone bought the item - twice. Not realizing, of course, that it was the same item.