I agree with you all. I know how to produce both astringency and diacetyl with my process and also how to prevent them. Both faults are mouthfeel, not flavors. I had problems with astringency when I first tried brewing lighter colored beers (< 8 SRM). This was due to water chemistry issues, after dealing with it, I am now able to produce very good lighter beers. Diacetyl in lagers was an easy one to solve as well and I seem to be very sensitive to it. I will usually taste my hydro samples and during the first week of fermentation the diacetyl is off the charts for me (especially with 34/70 and WLP 820) and yes I ferment between 48 and 50 F. I do a diacetyl rest at 66 - 75% completion and it goes away completely.