As mentioned elsewhere in this thread, it's opt-in to avoid breaking existing behavior. But given that ingestion points are easy to identify, it's pretty straightforward to turn on (especially if you have a schema for your inputs): https://pandas.pydata.org/pandas-docs/stable/user_guide/inte...
I saw in implementation (CSV parser in Julia) were the sentinel value was randomly assigned at read time (if a value in the input was equal to the sentinel value, change randomly).after parsing, the sentinel value would be converted to the appropriate data type (Julia Missing)