I've been reading up on this issue from the perspective of weavers and spinners with the help of my local library. Here's some more random information on this topic.
I've read, but haven't confirmed with more than one source that it is very rare to find commercial knitting yarns that are plied in Z formation.
I also found one source that mentioned twined or two-end knitting is easier with a Z-plied yarn. I tried that technique years ago and didn't finish the project because the twisting of the two ends drove me crazy.
Double Moss stitch biases but the slant can be blocked out. Read a fascinating post on the topic here.
Left handed knitting is said to untwist normal yarns but tightens left handed
yarns with each stitch. (I need to start asking my left handed knitting friends some questions to more fully understand this).
Linen is normally made s-twist and z-ply
to take advantage of the natural twist in the stem of the flax plant.
Balanced yarns will lie flat and hang in a straight coil.
Biasing can be worse in seamless knitting.
Remember, lace knitting which biases is often due to repeating k2tog without a balancing decrease worked in the opposite direction.
turns out that weavers who refer to energized yarns, mean yarns which
have been purposely over-twisted. Energized
yarns will try to double back on themselves and will twist if held in a
coil. Weavers use these yarns for specific 3-D effects in
their work. Energized yarns (single or plied) will impart bias to fabrics. I think this may be why I've often been told that yarns for weaving will bias if we knit with them. This always confused me when I shopped in yarn stores which supply both knitters and weavers. The last time I asked I was told the yarns on cones were also available in smaller put ups for knitters.
As I think back over my knitting history I'm realizing that some of my project fails may have been due to my lack of understanding of the basics of yarn construction.