More specifically the problem was:
"Microsoft invented a variant of UTF-8 (that Python calls "utf-8-sig") for its Notepad program: Before any of the Unicode characters is written to the file, a UTF-8 encoded BOM"
using "utf-8-sig" as decoder format ignores it when absent and removes it when present
Some user wanted to input timeseries data there was an UTF-8 encoding/decoding problem : https://docs.python.org/3/library/codecs.html#encodings-and-unicode
More specifically the problem was: "Microsoft invented a variant of UTF-8 (that Python calls "utf-8-sig") for its Notepad program: Before any of the Unicode characters is written to the file, a UTF-8 encoded BOM"
using "utf-8-sig" as decoder format ignores it when absent and removes it when present