What gets fixed
Quoting is rewritten to the rule in RFC 4180: a field is quoted when it contains the delimiter, a quote or a line break, and an embedded quote is doubled. Files that quote everything, or quote nothing and hope, both come out correct.
Ragged rows are padded. A file where some rows have fewer fields than the header is common in hand-edited exports, and leaving it ragged means every downstream tool disagrees about where the columns are.
Whitespace around values is trimmed. A field written as ` name ` almost never means to include those spaces, and they break joins and lookups in ways that take an hour to find.
Encoding and Excel
Excel on Windows assumes a CSV is in the local code page unless the file opens with a UTF-8 byte order mark. Adding one is the single fix for the accented characters that arrive as garbage, and it is a checkbox here.