Both variations of the monowhip (plain vanilla and fingertip) have a weight on the end to give it mass and control, so you could A) grasp it by that, or B) buy rappelling gloves. I'm sure there are stylish ones available in 2075.
I would imagine using the monowhip to deflect the force of the blow -- you wouldn't *want* to slice, say, a sword on half on a Parry, as then you end up with two stab wounds instead of just the one.
(Also you can't do Called Shot: Break Weapon on a Parry or Riposte.)
I've seen many, many threads suggesting that monowhips are brittle and/or fragile, yet the materials these things would likely be derived from are neither. Even with current tech, most nano-fibers, tubes, and ribbons are insanely strong, and you can use the stuff as climbing rope in SR5...assuming you have rappelling gloves.
-Jn-
Ifriti Sophist