Texture Matrix - one stack for each unit?

I’m not sure if this is possible, but I would like to rotate a texture by 180 deg for unit 2 but not with texture unit 1 (using multitexture).

Is this possible using the texture matrix stack?

Yes, from the OpenGL 1.3 specs:

There is also a corresponding texture matrix stack for each texture unit. To
change the stack affected by matrix operations, set the active texture unit selector
by calling
void ActiveTexture( enum texture );

Nice. Thanks for that.