And yes I am Portuguese, born and raised and I do know what you mean, there are mistakes that are somewhat common for Portuguese speaking English and I do make an effort not to make the same mistakes. However I know my English is far form perfect and it's always easier when it's in written form. I think that the fact that I've always spent too much time watching american/british movies and TV shows made me pay more attention to how English should be spoken :).
But anyway, thank you for saying I speak perfect English, it's actually a great compliment. :)
This is not the case. Different people make different mistakes, as any exposure to a high-school level English class will allow you to discover. There's a case for clusters of similar errors, but then again any generalizing statement is true for a sufficiently high level of clustering.
I can see how you could draw that conclusion from my post, however. I assure you there was no intent to generalize.
One somewhat personal question, if you don't mind. You say you are Portuguese. Is English a second language for you? I don't see the telltale signs of a Portuguese -> English speaker (I have a lot of experience interacting with Portuguese speakers, and their English mistakes are pretty uniform due to the specific differences between the languages, esp regarding prepositions and tense). Your article, as many have noted, is beautifully written even for a native English speaker.