Can a reviewer feature his/her own answer?
Technically yes, but practically, they don't.
Reviewers have the ability to feature their own answers, but they never do.
Every reviewer that we've ever had on Socratic wholeheartedly agrees that featuring one's own answers is unethical, which is why we've never had a reviewer who featured his or her own answers.
In fact, contributors understand that when they become a featured answers reviewer in a given subject, their own answers in that subject will take the back seat to other contributors' answers. That comes with the territory of being a reviewer on Socratic, at least at the moment.
That said, we do have a system put in place to ensure that answers written by reviewers have a chance at being featured. We actually want to expand the program to include two reviewers per subject, which will allow reviewers to review each other's answers in a given subject, but that is not going to happen in the near future.