I am not sure, if this is a bug of the package showhyphens or some LaTeX-behaviour I don't understand. Please have a look on the following example:
% arara: lualatex
\documentclass[ngerman]{article}
\usepackage{babel}
\usepackage{showhyphens}
\begin{document}
\noindent Hallo\\Hallo
\end{document}
Could there be any reason to suppress hyphenation here? When using the babel shorthand "- the red hyphenation line is shown.


\\can be useful. Using\\in normal text can be justified only in very rare occasions. If\\is in the scope of\raggedright,\raggedleftor\centering, the hyphenation point is found. – egreg Nov 20 '13 at 12:05\\s. In daily business, I just never use those back slashes. – LaRiFaRi Nov 20 '13 at 13:02\\in\raggedright, which is essentially the same, because in that context\\issues\par) is better. – egreg Nov 20 '13 at 13:04