Should I be concerned about someone removing a watermark I add to my image? Are there steps I can take to ensure that it's not possible?
Can someone remove the watermark from your image? Yes, of course.
Is it easy? No, not without the right tools
Just like with any other area of human endeavor, it's an arms race. Whatever protection can be devised can be circumvented. Whatever attack is known, can be defended against. It's a never-ending cycle.
A watermark on an image keeps honest people honest, just like a lock on a door. But a watermark (or any other security scheme) will never protect from someone with true larcenous intent.
A good question to ask is: How much value do I place on this image, and how much time and money do I want to spend to make it a little harder (not impossible) for someone to use without my consent?