Finally, after a long waiting (~50 days...), they replied my inquiry regarding the rejection. I've posted my RA letter here before. For those who do not remember my case, please just check my previous posts. Long story short, the case is closed. Regarding the RA referefence letter, the lesson learnt is to emphasize that you "assist your professor", even though it is your thesis...
Here is the response I got:
"Your application for permanent residence in Canada in the Federal Skilled Worker Class was considered on its substantive merits but was refused. You were provided with the decision containing the reasons for refusal of this application in our message thereby fully concluding this application. The documents you provided do not list actions which are described in the lead statement and a substantial number of the main duties under the NOC code you selected. We note that it does not mention that you assist university professors in research activities, but rather your main duties were conducting research and report writing, especially your doctoral thesis."
Anyways, I'll plan to apply under CEC once I get my one-year work experience with my work permit. Tired of playing with the word games. Good luck to the rest in the forum!!