An interesting idea, but I can't help but feel this is a terribly flawed approach. You need to develop your own voice, not write according to such a simple theory. Varying the complexity of your sentences - as well as length - is what keeps a reader from falling asleep.
Some people prefer the use of passive voice to avoid implicating certain individuals. Or for hiding their involvement or confidence. Other modes have their time and place as well.
I'm fairly certain that if you never looked at the usernames, you could still distinguish which posts are mine from style alone. I show the same mannerisms in speech as well.
Games of imagination are never truly done. Yet tomorrow we shall start another one.
Its a nice idea. Of course you dont have to use it, but it can help to make your writing more comfortable. If you are writing roleplaying games its good. Keeping things understandable is important. If you are writing a novel you should find your own (but understandable) style.
I for one am terrible at avoiding a passive voice. I've simplified my sentences quite a lot. Apparently I use a lot of adverbs which is for some reason a no-no.
I'm tempted to submit my essays to Hemingway for review. Academic writing is notorious for using the passive voice. Yes, I know that Hemingway won't fix everything. After having to relearn English, I can honestly say that every little bit helps.
I seem to recall similar nonsense with the version of WordPerfect I had in high school. It had a subroutine (shakes walker at the term "app") that would "grade" whatever you had written. Much hay was made of the fact that the works of Hemmingway, ironically, graded at the primary school level.
Much like several other people have stated, I tend to write how I speak.
When all you have is a gun that fires windows, every problem looks defenestratable.