import std.stdio;
void main()
{
 writefln("%a", -0.0);
}

should print -0x0.p+0, but instead prints 0x0.p+0.
Clearly, it's using a "<0" test for the sign, when it should be using signbit(). Also applies to the %A option. The %f, %e, and %g formats work correctly.
This is actually a DMC library bug, so it applies in many places.
DMD 0.145 Windows. Probably doesn't occur with GDC.
(I don't think this really belongs in DStress, since it's a DMC bug, not a D bug).

You're right, it's a DMC issue, and the fix for it will go out in the next DMC update.