I’ve modified the pattern to be no-purl, not because I dislike purling but because it lets me slip stitches on both sides. By doing this my “wrong side” looks like the original pattern’s “right side”, and my new “right side” has even bigger, more graphical carry-along loops of yarn. The two sides aren’t identical, but I think of it as a more reversible version, because both sides are equally pretty and graphic in their own way.

To clarify the pattern mod - whenever you see purls in the pattern, you should instead slip pwise wyif. For example, the original Row 2 of the Prismatic reads:
Row 2 (WS): k3, *p2, k3, p1* to last 3 sts, sl3 pwise wyif.

My Row 2 is:
Row 2 (WS): k3, *sl2 pwise wyif, k3, sl1 pwise wyif* to last 3 sts, sl3 pwise wyif.

In the body of the scarf you’ll always be slipping 3 sts pwise wyif. The first time you encounter purl/slips at the beginning of the row it may be 1 or 2 instead of 3 sts, depending on where you are in the overall 12 row diagonal pattern repeat. At the end of the row you’ll be slipping anywhere from 3 sts (just the I-cord ones) to 6 sts (the I-cord plus a full 3 st pattern repeat) depending on where you are in the overall 12 row diagonal repeat on that particular row.