Unpopular opinion: I switched from a bone folder to a teflon folder for my leather work and I'm never going back.
I used to think the traditional bone folder was essential for creasing and smoothing, but after my friend in Seattle swore by her teflon one for preventing marks on darker leathers, I tried it on a custom journal project last week and the difference in the finish, especially on navy blue calfskin, was honestly shocking.
Ever think about the sound? My bone folder has this sharp scrape that makes my teeth hurt on dry leather. The teflon one just glides with a quiet shush, which is weirdly nice when you're working late. It feels less like forcing the material and more like guiding it. That alone changed how I work on thin pieces that used to buckle.