Related: Fake explanation, Guessing the teachers password, Understanding your understanding, many more
The mental model concept gets used so frequently and seems so intuitively obvious that I debated whether to bother writing this. But beyond the basic value that comes from unpacking our intuitions, it turns out that the concept allows a pretty impressive integration and streamlining of a wide range of mental phenomena.
You should've waited for the article to get promoted, and it seems it's not going to be. Currently, the concept is not clearly explored or motivated on the blog.
I think mental models are interesting for being mechanisms, rather than merely classes and instances. I suspect we may refer to the concept again, in which case a brief definition on the Wiki linking a straightforward elaboration such as this is useful.