This is an issue that's been bothering me for a while. I'm interested in typesetting poetry on narrow pages. I'm using the verse package to set the poem and the geometry package to manage the page size. When the length of a line of text just reaches the margin, a vertical space is inserted below the line.
Here's my minimal example:
\documentclass{article}
\usepackage[paperheight=10in,paperwidth=5in,margin=1in]{geometry}
\usepackage{verse}
\begin{document}
\begin{verse}
% Works how I expect:
The quick brown fox jumped over the\\
Lazy dog.
% Make first line a bit longer, and now there is extra space between lines
The quick brown FOX jumped over The\\
Lazy dog.
\end{verse}
\end{document}

