Foreword:
Everyone who's reading this I'm sure has roleplayed at some point in their life. This is the spelling out of a thought I had while answering a question. Namely, what makes for good posting, good threads, and generally fun roleplaying? This is merely a theory I came up with, and it is still incomplete. There is always more to be said about the art of writing, the art of storytelling, and the art of roleplaying. If you have any questions, comments, or concerns feel free to post them. If you'd like to mesh the idea into a more universal theory feel free (although being credited would be nice). If you disagree, I invite you to be vocal about it, just be civil. Credit goes to Carta for the diagram because I'm lazy. Further thanks to Carta, Motuka, and Zoingo for proofreading and suggestions.
The Compass:
To begin this theory, I will state that all posts and all threads can be charted on a two dimensional, x-y chart. For our purposes, the y-axis will be Creativity, with the top being more creative, and the bottom being less so. The top would include original works, brand new ideas, new characters, new situations, anything that hasn't been done before. The bottom would include ideas such as Captain Cliche, Lord Generic, and a considerable portion of what can be found on TV Tropes. In essence, the bottom is cliches and overused ideas and topics. The x-axis is the common sense. Rationality, Reasonability, and Realism. The right is where rational, reasonable, and realistic thought processes and actions happen, where numbers make sense. Things on the right simply make sense. The left is where we get terms including "number wanking", "godmodding", and other ideas that nobody wants to be associated with.
Creativity:
I think everyone can agree that something that is unique and creative makes for better reading than something that is bland and overused. Creativity I'm going to loosely define as being unique, original, and/or unusual. This is why I enjoy reading dystopian fiction; it's fun reading all the different visions people have, the different interpretations, and the different viewpoints. The idea of creativity can apply to the characters, to the setting, to the mood, to the writing style, to almost all aspects of the piece of writing. Creativity is also a relative scale. There are many times that I see groups of writers storytelling within confines previously set up, for instance fanfiction. While I can't say I've read much of it, I know there is creative fanfiction, where they take barely mentioned characters and give them a story, or take the characters on adventures of the established canon. These can be creative in a relative scale.
Something can be creative without being entirely original either. You can take a well known idea; for instance, the story of Romeo and Juliet can be used in a variety of different settings and seem original and fun and creative. Place a story like that in the Star Wars universe, or the LOTR universe, or something else. There are no set rules for being creative, but creativity is easy to recognize. This indefiniteness is partly why the diagram above has no numbers; there is "high" creativity and "low" creativity, sorta like how there is no strict definition for someone being "tall." You can be relatively tall, or you can simply be tall; there is no set height. Anyway enough digression.
Common Sense:
Similarly to Creativity, I believe it's pretty easy to determine if something makes sense. While traditional and time-tested customs here on NS in regards to population and other hardcoded aspects of the game are generally accepted (for instance, the 100 million population to have nukes guideline [this is NOT a rule by any means] or the .5%, 1%, or 5% [depending on the group you play with] population limit on your nation's military), there are some roleplaying aspects which continue to be put to the writers discretion. Before I go further on this idea, I must again say that common sense is a relative scale. In a world of magic, common sense regarding the laws of physics doesn't necessarily apply, so realism based on real world physics doesn't always have to be there. In a story about an insane asylum, the people will not always be making normal actions or having normal thought processes, so your character doesn't necessarily have to follow "rational" thought processes.
But this doesn't mean you can throw these ideas out entirely when you write in these unusual circumstances. In a world of magic, the physics tend to have CHANGED. They still exist. You still should be realistic within the expanded boundaries. In an insane asylum, the rationality of the character has CHANGED, they still believe they are being rational. Be rational within this new set of boundaries.
Now that that's better explained, have your story make sense. If your setting is modern or historical tech, an excellent set of expectations of common sense has been set up by the community and past roleplayers. If your setting is anything else other than modern or historical, you have a little more freedom with common sense. Just remember that everything you do only expands or changes the boundaries, there are always boundaries in good writing.
An idea added by Motuka, which I agree with (with the exception that it really only applies to writing with multiple authors or roleplaying, writing by yourself this is less of an issue), is common sense applies OOCly as well as ICly. Unless everyone agrees, don't try and give yourself an instant win option, regardless of how well it's explained ICly. It removes the fun. An example he provided would be "we have slipstream drives on our space missiles, so they can just disappear from inside my ships and reappear inside your defenses."
Bringing it Together:
Now on these two scales, Creativity and Common Sense, we can agree that the more sense and more creativity that is involved makes for better writing. Holding all other things equal (such as length, grammar, syntax, diction, prose, eloquence, rhetoric, etc.). So if the further right we are, the better the writing, and the further up we are, the better the writing, thus we can conclude that everything in the top right quadrant contains the best writing. It makes sense and is creative. This is not saying that the first quadrant is the only place where good writing exists, simply the idea that the further up and right something is, the better it is. This isn't that hard of a concept is it?
Clarifications:
Now from this it might be interpreted that I favor or encourage technical writing because it makes sense. This is not at all true. I personally don't give a rat's ass how your gun works. I do care that if you shoot someone with it, they sensibly respond to getting shot, be it stopping the projectile somehow or taking casualties.
It can also be interpreted, that this means that a one-liner that is both creative and sensible is better than a full post that is less creative and sensible. To this I reply, while rare, this is possible, and I would like to point again to "all other things equal". It is possible a one liner is most appropriate for a reply, and in this case I would say yeah, a one-liner is better.
Here's another article I wrote, enjoy. Comments, questions, and concerns are welcome.