This question has already been asked a couple times: here and here*. Those question's answers do not satisfy me, however, and I think it is a slightly different issue. Besides, I'm using Illustrator CS6.
Say, I have a white object on a coloured background:
And I apply a clipping mask to it like so:
No matter my colour settings or way of exporting, I tend to end up with very visible coloured lines marking the places where the mask cuts off the white shape:
Is there a way to avoid this glitch? Oddly enough, it doesn't pop up when I punch out the object and then clip the resulting punched shape and place the result on the regular white background.
The fact that the offending line is lighter than the actual colour I use, makes me think it has something to do with pixel alignment. I do, however, kind of refuse to work with pixel alignment, because it prevents me from exact positioning. And I wonder how I would have to solve the issue on a clipping mask that is, say, hexagonal:
*Scott/SOIA's solution to this question, unchecking 'Anti-Aliased Artwork', doesn't do the trick for me, especially when exporting to *.jpg.