> should be asking the user to select explicit input and output formats

It depends on the requirements.

If you're hired by a company to convert millions of old textfiles, they might want you to do it as well as possible using heuristics without any human input as a starting point.

Unless the input is such garbage that asking the user is pointless (like a lot of web sources) and fixing manually is too time expensive.

It becomes easier to just use https://pypi.org/project/ftfy/ on the input.