I have always made the assumption that if you post an image online, no matter what website, there will be ways that people can download it and then re-use it.
Some sites such as Facebook and Tumblr make it extremely easy for users to download posted images in whatever resolution they were uploaded albeit with some probably loss of quality due to the web site’s image “viewing optimisation” process.
Many online image hosting websites like 500px.com also offer to automatically apply an ugly watermark to your images (or you can do this yourself in Adobe Lightroom, etc before uploading them).
Google research has just posted a blog on how AI software can easily and automatically remove most watermarks effectively – see HERE for the post.
It seems that if you want to make it harder for AI to do this, you not only need to introduce randomness to the position of the watermark but a random warping of the watermark.
I guess randomly warped watermarks will come in future versions of Lightroom – but for now it seems that all your efforts with watermarking may be in vain and just makes your photos ugly.
So current state, your watermark will be easily removed thus assume once uploaded, there is a risk others could abuse your image copyright without your permission.