I observed a user on https://sqa.stackexchange.com/ who was several time asking questions and then accepting its own answer. A couple of the questions are asked and answers accepted exactly at the same time. One of the questions was asked and answered on 'Mar 17 at 8:39' , the second question is asked and answered on 'Mar 21 at 16:07'. My assumption is that person was just gaining points of reputation. What is the best action to take now?
Great question. I'm glad you asked. It smells like something that's bad. But what should we do?
Nothing. The system is working as intended.
Asking a question and posting an immediate answer is one of the intended features of Stack Exchange. Basically, the original visions of Stack Overflow (which evolved into Stack Exchange) is a special Venn Diagram of existing services. In this case, it seems like this user is leveraging the Blog corner of the diagram.
If the question is good (forget the self-answer, focus on the question) then the question deserves an up-vote. If it doesn't, it deserves a down-vote, an edit, or a flag.
If the answer is good (forget that it's also asked by the guy) it deserves an upvote. If it doesn't, it deserves a down-vote, an edit, or a flag.
If the user has posted junk questions or answers, they should get handled separately.
If the user has posted valuable information that will be useful to future visitors... where's the problem? :-)