RE: Difference between EM QUAD and EM SPACE

[Jonathan Coxhead]

   In TeX, the difference is that an EM QUAD (\qquad) and an EN QUAD 
(\quad) provide spaces that are legitimate breakpoints for lines within a 
paragraph; while EM SPACE, EN SPACE (\enspace) and THIN SPACE (\thinspace) 
produce horizontal space that cannot cause a line-break.

   My assumption on reading the Unicode standard was that this was the 
intention---though it is not spelled out anywhere. Maybe a clarification 
would be worthwhile. If so, the fact that TeX is so widely implemented and 
used---at least within the arena of technical documents---might make it 
worthwhile to preserve those characteristics.

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