@godbyk: Hi - would you by any chance see a way how we could move the \setlength{\emergencystretch}{1em} into, say, the note environment, or even set it globally? All my attempts to move those length changes away from the lines that immediately need them have failed.

@tkoeppe I think the \emergencystretch would apply to the entire paragraph the note is a part of. We could apply it to the note (and its surrounding paragraph), put the note in its own paragraph and apply it, or apply it globally.

You can also try out the \sloppy and \fussy macros. The former relaxes TeX's typesetting standards a bit to allow for looser line breaking. The latter resets the values to TeX's default. Their default definitions are as follows:

\def\sloppy{%
  \tolerance 9999%
  \emergencystretch 3em%
  \hfuzz .5\p@
  \vfuzz\hfuzz}

\def\fussy{%
  \emergencystretch\z@
  \tolerance 200%
  \hfuzz .1\p@
  \vfuzz\hfuzz}