On (info "(texinfo) Footnote Styles") (info "(texinfo) @paragraphindent") mention how to unindent footnotes. $ makeinfo --plaintext --set-customization-variable paragraphindent=0 doesn't work.
Your invokation of makeinfo is incorrect, so what do you expect? GNU makeinfo takes a mandatory file name as an argument. Or mention that 'sorry, it is impossible. Use sed or awk etc.' It is mentioned, in the error message.
