It is not a feminist statement no matter how much you think it is. Wearing niqab does erase you from society. That’s what it is designed to do. It is the product of imposed laws designed to strengthen male dominance.
You can make it quirky here and have fun with it; good for you. It certain parts of the world you would be in major trouble with the religious police over that.
I am glad you have found a way to enjoy it. In doing so, you have a mechanism that does not make you feel repressed. Those outside looking at you believe you are repressed because you are hidden from them. It’s the ‘I can’t see the forest for the trees’ problem. You cannot see how your mode of dress looks from the outside.
The people who talk to you are concerned about the freedom of people to be seen. You can freely choose not to be seen but it is not healthy and people are genuinely concerned about that. Their concerns are valid.