[XeTeX] shrinkability and stretchability of interword space with default monotype font

[jfbu]

Hi,

some years ago I noticed that the interword space with the 
default monotype font had some stretchability and shrinkability,
which results in problems in verbatim environments when
the line is long enough to go into the right margin.

I raised an issue there

https://github.com/wspr/fontspec/issues/139

which was not very well formulated, and besides I probably
posted at the wrong place, as this isn't a fontspec issue, 
as stressed again by recent comment by David there:

https://github.com/wspr/fontspec/issues/139#issuecomment-174298868

Should I raise an issue on http://sourceforge.net/p/xetex/bugs/ ?

please CC to my address as I don't currently subscribe to the list,

best,

Jean-François