portability of quote marks

[Doug McIlroy]

M4 uses ASCII character 0x60 as a left quote. Revisions of the ASCII
standard have variously identified this character as "left quote-grave
accent" and simply "grave accent", and have warned that it may
have different interpretations internationally. Has this
ambiguity affected the use of m4 outside the US? If so, how?

(An aesthetic effect, felt even in the US, is that left and
right quotes may be quite unsymmetric, depending on the type
font in which programs are rendered. This has the unfortunate
side effect of deterring use of identical text for testing 
and for publication.)

Doug