If you have not done so already, please read the example post, and then read this.
This should not require an explanation post; it is perfectly clear what would cause the blogger to be identified as Tom in Mrs. Doe's class.
First, he said his name was Tom and he was in Mrs. Doe's class. Second, he described an incident that occured in her class to him, and as such even if he did not mention his name it would identify the writer as Tom.
Ignore the overall content of the blog post. That's not what's important. This is only meant as an example of how a blogger could be easily identified by a reader.