Someone's writing style/voice is an amalgamation of their word choice, sentence structure, and proclivity for certain writing elements, like complex/simple sentences, and so on. You can break it apart very easily, but a lot of it is just a matter of qualitative reasoning, if you're observant enough—reading and checking to see if it sounds like the same voice. I've actually recognized the identity of a writer by just reading a few sentences. I am confident in my analysis of just reading a few of their post.
I would recommend not responding to them and just place them on ignore.