See this thread (started by yours truly). The latest Consumer Reports Car Reliability Survey came out yesterday, and BMW ranks ninth -- considerably above average -- and the 2 Series is rated as the most reliable BMW by a fair amount. In fact, the 2 Series has now been rated the most reliable car
in its class for three years running.
Keep in mind two things:
1). The 2 Series has been around since late 2013. There is now plenty of data on the line, particularly pre-2017 Nxx-engine models.
2). By its nature, forums such as this skew the perceived reliability of a car downward because, by
their nature, people complain far, far more than praise.
A related aside to 2). above: The most reliable car in the 2016 survey is the Toyota Prius/Lexus CT 200h. I owned a CT200h F Sport before getting my 2 Series. I was a member of a couple of forums for the car. There was plenty of conjecture about things going wrong in others' CTs; that's partially what forums are for, you know? But the bottom line is that
the CT is the most reliable car money can buy. Period. This is not opinion. This is fact based on empirical statistics.
So basically, if you're worried about reliability, you should be worried more by any other competing car rather than the 2 Series.