You are right, at this time blogging is only authorized for TI employees.
The reason that is shows up under the ranking points system is we do have the ability to grant community users the ability to blog, should we desire, We have been reaching out to people to guest blog on our site.
An example of this is the "Embedded Insights Question of the Week" with guest blogger Robert Cravotta
He gets points as a community member when he posts a blog.
Foe - Texas Instruments WW Community Program Manager