For approximately three and a half years, this method has worked fine for me. I may have encountered characters who were similar tropes or works with similar concepts to my piece (for example, Ben in Aerin's Standing in Fire is kinda manipulative like Kaden in my story, but he's certainly an original character) but until yesterday, I have never been plagiarized.
I am trying to get this situation dealt with, but it has made me realize that perhaps making my work available publicly online isn't working anymore. I've made many friends, on the site as well as through writing conferences, who would be willing to help me with my pieces and give feedback. Since I now have this network, I am deciding to make my important pieces on Figment private and only give some people the access codes. Additionally, on the other sites Wattpad and Hexbound, there is a "followers-only" setting for new stories that I will be applying. It's by no means a perfect system but it's a lot better.
If you read my pieces on Figment, and you would like to have the access codes, please comment below indicating that, and put your email address in the email field (which doesn't show to other commenters). I will create a Google Document with any new access codes for my pieces. I will not be transferring everything over, just certain things. There will, of course, still be pieces available on Figment, but they won't be ones I'm serious about (ex. the Humor Shorts or contest entries.) I promise not to use your email for spam.
Thanks for understanding!
*If you are from Figment, please use your name from there in the name field.*