My client has a problem with moisture collecting above the ceiling from a exhoust fan above the area. Should there be anything there to wick the moisture away or is the problem with the exhaust duct?

Maybe the moisture is from condensation on the exhaust duct, especially if it's a rigid metal duct. Perhaps any joints in the duct should be sealed with tape, and then the duct could be wrapped with insulation, and that could end the problem.

Are you sure the fan is being vented to the OUT side of the house? Sometimes they aren't.

There is still some controversy about how practical a bathroom exhaust fan may be. Since the school of thought I align with suggests that they remove air and only a miniscule amount of moisture I belive the warm air in the duct is condensing the cool air in the attic and dripping moisture onto the surface above the ceiling.

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I belive the warm air in the duct is condensing the cool air in the attic and dripping moisture onto the surface above the ceiling.

Nice theory, but backwards physics. Warm air in the duct would actually inhibit the formation of condensation outside the duct. However, when the duct is cool, it could be a surface upon which water condenses,

There is no question about the benefits of exhaust fans in areas of high moisture. I don't know where the theory that a fan removes little moisture originates, but I believe it is incorrect and misleading.

I gave up trying to run moisture exhaust fans through unconditioned space before expelling outside. Everything we do now goes out the gable end and is not exposed to any cold air until it hits the outside. I even slope the last foot of flex pipe downward before it goes outside just in case there is a little condensation in that section of the pipe, it will just run out the pipe to the outside.