Lens manufacturers say that anything other than a microfiber cloth will damage the coatings on a lens. But microfiber cloths eventually pick up crap and they look like they're a pain to wash.
How do you keep your lenses clean? Are you using cloth/kleenex or microfiber cloths? If you use microfiber cloths, how do you clean those?
None of them are hemmed, because they don't fray. If you're worried about it, try gently rubbing at the edge of it. Threads won't come off in your hand either. Microfiber is just the size of the thread used, these are 100% polyester and completely machine washable.