Allen,

          My posts in Portuguese also gets polished sometimes. I never really learned the rules that apply to accents in Portuguese and I also misspell certain words.

           Perhaps the reason for the corrections is that in certain posts, like the ones I contribute, the mistakes may not be so evident for a non-native Portuguese learner since the post seems to be written by a native speaker. Hence it would be confusing for a Portuguese student, the site also caters to those learning Portuguese, to identify the mistakes.

           I think, for example, it would be like Dale, if English had accents, getting pretty much everything right except the accents and some words. In this case it seems to me that an English learner would be less likely to question possible mistakes since he or she kind of takes it as a given that the person who contributed the post is a native and so the post must be written correctly.

         Anyway that is my guess regarding the polishing of certain posts.