First of all, I don't care much for some philosophical dictionary's definition of simplicity. You are going to have to specify what you mean by parsimony, and you are going to have to specify it with maths.
Here's my take:
Simplicity is the opposite of Complexity, and Complexity is the Kolmogorov kind. That is the entirety of my definition. And the universe appears to be made on very simple (as specified above) maths.
The Heuristic I am referring to is: "There are many, many, many occasions where people have expected the universe to conform to their sensibilities, and have been dead wrong." It has a lot of evidence backing it, and QM is one very counter-intuitive thing (although the maths are pretty simple), you simply aren't built to think about it.
QMI: Quantum Mechanical Interpretation
Lastly: Have you even read the QM sequence? It gives you a good grasp of what physicists are doing and also explain why everything non-MWI-like is more complex (of the Kolmogorov kind) that any MWI-like.
No, I'm not defining a notion based on anyone's whim/sensibilities; I fully agree that, to be meaningful, any account of 'simplicity' must be fully formalizable (a la K-complexity). However, I expect a full account of simplicity to include both elegance and parsimony based on the following kind of intuition:
a) There is in fact "stuff" out there
b) Everything that actually exists consists of some orderly combination of this stuff, acting in an orderly manner according to the nature of the stuff
c) All other things being equal, a theory is more simpl...
I was very interested in the discussions and opinions that grew out of the last time this was played, but find digging through 800+ comments for a new game to start on the same thread annoying. I also don't want this game ruined by a potential sock puppet (whom ever it may be). So here's a non-sockpuppetiered Irrationality Game, if there's still interest. If there isn't, downvote to oblivion!
The original rules:
Enjoy!