Yes, you can plumb the exhaust in any direction, but those extra turns and duct length will add resistance to what the fan has to push. It's a good idea to increase the duct size or cross-sectional area of the duct in such instances (I've run 3 1/4 x 10 rectangular duct in walls as an increase for 6" duct). If you need a larger wall vent because of this, American Aldes makes larger units, and they have a magnetic seal on the flapper that works MUCH better than what you get in the box stores. Here is a link that might be useful: American Aldes wall vents

OK...problem is now resolved (I think). I managed to get the cover and light fixture out of the unit, then removed the fan assembly to see if I could see things better. There is a contra-flow "flap" that was stuck in an open position. I could close by pushing it shut with a screwdriver, but then when I opened it again, it stayed open. Perhaps some lint build-up or something like that, but anyway, there was a plastic tab that is to act as a counter-balance to make the thing shut again so I attached a small paper clip type thing to it to give it just an extra bit of weight. Now when I push it open with a screwdriver, it opens and then closes back on it's own. As for the venting piece, I really can't see if it's venting directly into the soffit, but I suspect you are right. It is so far back into a corner of the house, it's virtually impossible to see. Thanks to all for your help and advice. I love this kind of teamwork.

I live in a highrise and have just finished remodeling my kitchen. I, too have to change out the old micro with a new one that comes with the recirculting vent. It was the only option I have because of the house rules and the lack of space in my kitchen. Not sure if your condo's association would allow you to open up the ceiling to install an exhaust vent. If you live in a condo its likely your kitcen may not even have any ventilation system build in. Check with your resident manager or the association and obtain a floor plan for your unit or building. It will help you see the electrical and piping of your unit and gives you better idea what can or cannot be done. Hope this helps.

Brickeye thanks. For the record my statement on the neutrals all being tied together was incorrect. The load side of my GFCI feeds a protected outlet in that bath while that outlet feeds two protected GFCI outlets in a downstream master bath. The line side of the first GFCI is multipled to feed a fan and a ceiling light, and those neutrals on the line side (not load) are tied together. Nothing coming off the load side is multipled to non-protected devices. BTW the use of dielectric grease on that Broan QTR140 exhaust fan motor connector seems to have fixed the problem if their was leakage to ground. I still do not understand how moisture on what is now an unprotected fan (multipled on line not load side) causes the GFCI to trip. The load side is an entirely separate circuit. My original thread on this below is confusing because the tripping problem caused by the fan seemed to be fixed several times only to re-occur. Sealing the connector on the fan seems to be a cure for now. I wanted to tie up loose ends for others on these forums if appropriate. Here is a link that might be useful: Original thread on this