# Use case for pdfTeX's \quitvmode

While reading one of Lev's answers, I encountered a pdfTeX primitive \quitvmode that I have never noticed before.

The pdfTeX manual states that this causes TeX to leave (internal) vertical mode and enter horizontal mode—the mode in which TeX is building paragraphs. This is the purpose of the plain TeX and LaTeX macro \leavevmode. The manual states that this does so without any bad interaction with \everypar.

The only examples I can think of where this would be useful are horribly contrived. For example,

\everypar{\foo}
\def\foo#1{{\tt\string#1}}
\leavevmode foo

\quitvmode bar
\bye

produces

which is more or less what I'd expect, but this use of \everypar is really silly.

What is an actual use where using \quitvmode instead of \leavevmode matters?

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