No! My children were taught to respect books. The thought of a ripped book is total anathema to me!
Akin to people turning down book pages. WHY? WHY? WHY? Have you not even got a scrap of paper to use, let alone a proper bookmark? If I find a page so desecrated, I'll 'iron' it flat, but the crease can NEVER be fully removed!
If I come across a lovely card, I'll buy to use as a bookmark!
Have heaps of differing bookmarks I've collected over the years. If have excess, I donate to local library. They give them to their elderly customers' to use.