documentation of read_csv producing NaN floats in string column
There are a good few issue reports around the surprising behaviour of read_csv when reading empty cells and/or cells containing one of the special NaN strings with dtype=str, including n/a, null and NA. This behaviour should be documented in the description of the "dtype" parameter as this is what most people will read who encounter a type error. Ideally, there should also be pointers to workarounds, for example setting na_values = [] and keep_default_na = False seems to fix the problem with non-empty strings.

Related (incomplete list): issue #4849, issue #10205, issue #10647, issue #16569, issue #15669