Assuming a user has two accounts in SE (account A & B).
He asks a question using account A. Answers it using account B. It's not just answering, the answer is just "fantastic" - thus it has drawn votes from 15 - 30+. This is different from asking a question under one account and answering it using same account.
There is a scenario with pattern found within VBA tag.
When noticed, most of his questions are either duplicates or have been closed by community with closed line: "not clear, off topic" etc. The question and answer seem to have quite distinct same formatting.
Bottom line, it seems like the OP is trying to promote oneself within the SE. Isn't this defined as against SE moderator/review rules?
Personally I benefit and enjoyed his answers though.