It's sharp right? And it looks like it would be possible to cut with help of it? Looks like that to me.Also you don't have always knife with you when you find fibers, but.. there is change that you find flints Make it possible to cut fibers with flint, one more usage for it.
There was a similar idea.http://fodev.net/forum/index.php/topic,21766.msg179884.html#msg179884
flint was used to make (!) sharpened spear, so i wonder - can it be used for cutting fiber, because iron blade is way more hard to sharp then cut fiber from plant
How about just ripping the plant from the earth...