Regarding the "Aspirin as a blood thinner" theory: I'm not a physician either, but AFAIK there isn't any serious, properly controlled study that backs up the theory that the short-term blood-thinning effect of Aspirin has a long-term positive effect on stroke risk. Even if there was, consider the logic behind the recommendation. Most strokes occur because either high blood pressure caused a blood vessel to rupture, or there has enough plaque accumulated in one's vessels so that a lump of it breaks loose, travels through the blood stream, and clogs up a smaller vessel. The main risk factors are high blood pressure in the first case and atherosklerosis (hardening/narrowing of blood vessels) in the second case. Both risk factors are caused by diet (and genetic factors, but diet is the main contributor). Now, think about it: Even if Aspirin might make the blood thinner for some hours, does it really make sense to recommend it it as a prophylaxis against strokes when it just makes the blood flow somewhat smoother for a few hours? Wouldn't it make much more sense to change one's diet and prevent the high blood pressure and plaque buildup in the first place?
Regarding black chocolate as a blood thinner: Black chocolate contains less sugar than other chocolate, but more fat, which in turn is the main contributor to the clogging up of blood vessels. Any short-term blood-thinning effect of black chocolate is certain to be overridden by the long-term detrimental effect of fatty food. Put simply: _If_ black chocolate has a blood-thinning effect (which I don't know), then - by eating it - you'd basically increase your risk of getting a stroke later, but decrease the risk of getting one in the next three hours or so. I'm not sure if that's that good a deal. ;)
Regarding the linked article and whether it "praises medication that causes strokes" - it doesn't really, and I think (sorry) that that's a rather silly way of looking at it. Yes, strokes can occur under Ibuprofen, under certain conditions and if the risk is already high. It's debatable whether the medication "causes" such a stroke, or just makes it happen earlier due to creating even more "favorable" circumstances for one. But my man point here is another one: If you think that Ibuprofen should not be recommended because it "causes strokes", then you really cannot recommend any medication at all. Every medication has side effects, lots of useful and life-saving substances can be fatal if given to the wrong person, in the wrong circumstances, or in the wrong dosage. What matters is how well such fatal side-effects can be prevented. In the case of Ibuprofen, such prevention is very easy - simply don't take it continuously in large doses, and don't take it if you're sporting risk factors for stroke already. And, as for any medication, don't take it without consulting a competent physician who ideally knows you from experience.
