Such things that are specified for example on the Wunderground website here in the "Personal Weather Station Installation Guide", such as: where to place it depending on the environment, at what height...etc. All of the criterias that are given standing for keep a standard predetermined accuracy. In case of these conditions are not met with the given criterias, it will lead to inaccuracy, and obviously these weather stations will not be reliable at all. (as @Tomber42 said in his reply)
Anyway I absolutely agree with @Tomber42 because it's trivial that most of people looking at weather stations to get precise and reliable observation informations.. such as for example the Airports' weather stations are mainly the most reliable stations in my opinion.. and I can totally trust in it (because of it has regular maintenances, and operates under strictly specified standards).
And it would be nice if the same trust could be presented in the PWS's in the future, but imho that will need some installation criterias in the side of Windy.
If Windy would like to make it reliable and a good information source (such as now the most of weather stations), I think they should make a "Personal Weather Station Installation Guide" too, or something similar to that (as Wunderground did..), so those people who reported their PWS's should make those configurations that are laid down in the "Installation Guide", and their PWS's will appear just after that on Windy site.
To my mind, it would be a good solution to the all "PWS's unreliability and real data measuring" questions.
Btw, I don't say that this is a bad thing, I like it really much, and this "Observation vs forecast" feature is really unique and useful. But I'm just wondering what will happen with the newly coming PWS feature on the map.. And I just got this idea that I wrote above.
This is not an offense from my side, these are only some thoughts of the questioned area and potential ideas for the predictable problems.
Anyway I trust in Windy team, you guys always make really invaluable and unique features with a nice and clean interface. Just do it guys, as you always do!:))