Issue with em dash character

[Robert Voliva]

We're finding that, when working with the em dash character, the LEFT and
LENGTH functions don't work well together.  This query shows trying to
strip off the last character from a string containing an em dash:

mysql> select LEFT('031492349−0002,', LENGTH('031492349−0002,') - 1),
LENGTH('031492349−0002,'), LENGTH('031492349-0002,');
+------------------------------------------------------------+-----------------------------+---------------------------+
| LEFT('031492349−0002,', LENGTH('031492349−0002,') - 1)     |
LENGTH('031492349−0002,')   | LENGTH('031492349-0002,') |
+------------------------------------------------------------+-----------------------------+---------------------------+
| 031492349−0002,                                            |
             17 |                        15 |
+------------------------------------------------------------+-----------------------------+---------------------------+
1 row in set (0.06 sec)

Is this a bug?  If it's a "feature", what could we do instead to get around
this issue?

Thanks,
Robert Voliva