I don't know how you get 'This tactic is good for blah, see page blah' and take that to mean 'regardless of purpose' And the rules for how to target a square and what you do with it are on that page. And mention you have to be targetting a creature.
Out of context=bad.
Well, it says "This tactic is useful when...", not "This tactic can only be used when...". I would have thought the difference is pretty clear. The prior has no restrictive wording, so one can only assume its an example. The latter does have restrictive wording, and thus would be a rule.
And the rules for targetting are indeed on that page:
"If you want to use a power against an enemy, it must be within range and you must be able to target it."
Ok, only enemy creatures.
"When you use a melee attack or a ranged attack, you can target a square instead of an enemy."
This modifies the previous sentence, and changes the context. Its not out of context at all. The first tells us that we have to target an enemy, then the second tells us that we can also target a square instead of an enemy.
It's not explicit at all, it gives an example of when you want to target a square. There is no restrictive wording.No, it's expllicity used when you're trying to hit an invisible creature.
I have to disagree with you, but I don't think this argument will really get any further unless you can explain why you feel the rules don't mean what I think they mean. Btw I do DM alot of my games, and I'm answering this from a DMs point of view rather than a players.You're going beyond what the rules say, to what they imply. Deciding that is your DM's job.
As has been said before, while its not necessarily the behaviour I would have expected, the players are still expending a resource and it doesn't necessarily have to not make sense, so I'm pretty ok with it.