I might just be misunderstanding, but: with the new two-button approach to mirroring an object in the symmetry menu, left to right seems to mirror right to left and vice versa.
/edit: also, even when the direction is set to Y or Z, the buttons still say left to right and right to left. Maybe remove the “reset direction” buttons and add “top to bottom” and “front to back” (and their inverses) to the current two buttons?
It’s relative to the camera, it’s assuming your camera is more or less aligned with the symmetry plane.
Ahh, that explains it.
I personally feel like world-relative makes more sense, but since nobody else has mentioned it, I’m probably in the minority.
Thanks!
I’ve noticed this too.
Well it depends.
There are those who wants everything aligned and know what X, Y, Z refers to.
And then those who will hide the snap cube, use the trackball (with roll), and hide the grid.
Something I’ve been fixing is displaying an arrow on the symmetry line to show the direction.
But honestly it’s not high priority, you can simply undo and tap the other button.
Yeah for sure. An arrow would help, but it’s definitely not a high priority. 
Just think from models direction! If you are using rigs for animation, you have to get used to this anyway. Right arm is on the left if the model is facing you. 
I mean, that’s what would make sense to me. It’s the opposite of that, because the cube widget is mirrored (which I literally only just noticed, somehow). When “Front” is facing you, the “Left” and “Right” sides of the cube (which match the mirror operation’s left/right) are on the user’s left and right, not that of the model.
It feels like one of those things that’s like, a standard in other apps and so it made its way here. I’m just not used to it.
Cube is screen orientation, mirror is object orientation… 
At least I‘ll help myself this way.
just hit one, if it’s not, hit the other one 
