But all that matters is what I and those at my table think. If you disagree with our version of 'common sense', there IS no problem.
We don't all have to be playing every situation the same way.
This works only if you assume that you will always game with just the people at your table.
Allowing for things like people moving away, you moving away, you playing at a convention, you deciding you want to play in two games each week but your regular group doesn't, or any other change in the situation, we can assume that sometime in the future, it's very likely that you'll be sitting at a table with a group that includes some people who are not at your current table today.
Which means you will repeatedly need to rehash the "common sense" arguments over and over, each time you have a new face at your table.
And, as seems to be suggested by this thread, it's likely that some of those new faces at the table might have a different "common sense" than yours.
Which will cause friction, debates, even arguments. Unfortunately, it's hard to change people's common sense (I guess it's not really all that "common" is it?).
So, when this friction arises, and the difficulty of changing the new person's common sense results in a stand-off, the general solution is the DM says "well, since we can't find a 'common' ground, I'll just make a ruling and forevermore this rule is interpreted thusly..."
Which inevitably results in one of the dissenters being unhappy with the ruling.
Which undermines the "fun" - wasn't "fun" one of the cornerstone 4e principles?
All of that is a round-about path that gets us back to a principle of game design that I'd like to see more of in 4e, specifically, less is NOT more. Provide more rules. Provide clarifications. Avoid ambiguities. Make the rules as clear and concise and complete as possible. Eliminate any and all rules or rule conflicts that call for individual player interpretation.
Sure, I know that no game will ever achieve this 100%, but I do believe it should be a goal of good game design.
I'm hoping that as the months go by, WotC is compiling a very comprehensive list of issues and providing solutions for them that will be publicly available and downloadable as official rules corrections, changes, and errata - they've already made a small inroad to this; I'm hoping to see that become an errata superhighway.