@idefix37 You are absolutely right - after reading about MADIS, ingesting data from NOAA data sources and non-NOAA providers for delivery, I can understand that once the bad quality goes in, the bad quality also goes out to the "Meteorological Community", as they put it. Luckily, most of the distributed data does not fall into this category.
I will be more careful now, and filter out the PWS data which is often useless noise, unfortunately, and will also look with a certain questioning to some other stations as well, like those coming from ships. And keep my own boat's sensors well calibrated, allowing me to assess the models vs. the real weather situation, which is the purpose why I were looking at the stations around me in the first place.
Thank you for your insight.