What are your thoughts on soffit vent bath fan exhausts? What is the best way, in your opinion, to vent a bath fan and why? Around here, almost all new construction is done this way.
In my area this is acceptable. The gable is the ideal place to run a vent through.
· Improve: We noted that the exhaust duct for the main floor bathroom fan discharges the air through the roof soffit. This can promote mould growth in the roof space as a result of air flowing from the soffit into the roof space. It is better to run the exhaust duct through a gable end in the roof space or through a wall or roof. Equip the duct with a backdraft damper provided with weather-stripping and a counterweight or spring to prevent air return (“Clapet Daoust” type of damper or equivalent). Ensure that the exhaust outlet is not blocked, that the backdraft damper is working and closes properly, and that the air is discharged directly to the outside through a sealed, insulated duct. Make certain that duct is the size recommended by the manufacturer and is a short and straight as possible. Seal all leaks.
I agree with Marcel due to the geographical area.
Seen too many problems because of this in the Winter time. 
No moisture here, seen em vented into the attic after 10 or 15 years, no problem.