How do I remove bitter flavor from lime rind in soup?
You might be able to counter-balance it with other flavors (salt, sour, sweet, hot), but you're likely still going to have some bitter notes come through, it's just a question if it's tolerable or not, and some people dislike bitter more than others.  (I can't understand how people can drink beers other than lambics)

In looking at a similar thread on Chowhound, one of the recommendations is a bit of milk or cream.  If you're not lactose intollerant, it might be worth a try.

This could also be a chance for an experiment -- ladle it into a bunch of glasses, try some different things (sugar, vinegar, soy, hot sauce, milk, worcestershire, combinations of them, etc), and report back to us with what you think worked best.