Hey jd,
Yes, there is a study that indicates finasteride can cause reduced sperm quality. However, this article did not come to the conclusion that it could be permanent. I think they tested people after coming off finasteride and noticed things returned to normal.
Also, people that were affected by this already had low sperm quality. If you are concerned about this, get a sperm mobility test before starting on finasteride, and get this tested every year afterwards. If you find that you already have low sperm quality, then you might want to reconsider starting finasteride just in case. But for the 99.9% of young guys, this shouldn't be anything to worry about. Again, if something like this concerns you, test it regularly and keep an eye on it.
Are you talking about sperm quality during the initial trials? This was not reported, but I also doubt it was tested either. Again, like the whole debate about permanent side effects, this stuff has been on the market for 20 years. If a huge amount of people had their sperm quality crushed by taking finasteride, it would have been tested & confirmed in a lab setting and would be listed as a side effect by Merck. Everyone is basing this on a single study (there may be more actually, i've only seen one). As with all these studies, many people completely misrepresent the actual risk and ignore the scope.