How can I stop LaTeX from converting two hyphens to a single hyphen when loading package fontenc?

-- is a so-called TeX-Ligature which is converted into the n-dash. -{}- breaks this combination.

\documentclass[letterpaper]{article}
\usepackage[T1]{fontenc}

\begin{document}
A hyphen: \texttt{-}

Two hyphens: \texttt{-{}-}

Three hyphens: \texttt{-{}-{}-}
\end{document}

or define own macros for this

This approach didn't work for me in the bibliography, if you have the same problem simply insert one of the phantom commands:

@article{Foo,
  title = {Hello -\phantom{}- World},
}

This will work as desired.

For me, -{}- is not working for breaking the ligature in --. The trick -\phantom{}- works, but it is a bit wordy. I found that the command for the italic correction could be the best choice in this particular case: this -\/- works for me in every case.

Please see difference between {} and / for breaking ligatures for further details.