I'm not sure that the ability to have original thoughts is at all closely connected to the ability to think rationally. What makes you reach that conclusion?
Unfortunately there's a second observation - there's no reason to believe such people existed only in the past, or would have aversion to blogging - so if super-smart people exist, it's fairly certain that some blogs of such people exist. And if such blogs existed, I would expect to have found a few by now.
Have you tried looking at Terence Tao's blog? I think he fits your model, but it may be that many of his posts will be too technical for a non-mathematician. I'm not sure in general if blogging is a good medium for actually finding this sort of thing. It is easy to see if a blogger isn't very smart. it isn't clear to me that it is a medium that allows one to easily tell if someone is very smart.
To whom it may concern:
This thread is for the discussion of Less Wrong topics that have not appeared in recent posts. If a discussion gets unwieldy, celebrate by turning it into a top-level post.
(After the critical success of part II, and the strong box office sales of part III in spite of mixed reviews, will part IV finally see the June Open Thread jump the shark?)