I am all for pressing the fabric in the direction it makes sense....which is anyway it reduces bulk at the seams and what ever way it means the seams can "nest" together the best. I love patterns that tell me the way to press the fabric. It just makes the whole putting it together so much easier. Now, I have pressed to light and honestly, I can't remember a quilt where after I washed it and put it on the bed that I looked at it and said "oh my goodness...look at the shadow of that seam showing through". Not saying it can't happen, but I have never noticed it. I do use quilt shop cotton for the most part and don't do a lot of piecing with pure white fabric though. If you use light weight very light fabric, it could happen. but I wouldn't use that kind of fabric on a bed quilt anyway.