As an answer to What can be done to improve moderation of self-answered questions?, Jeff Atwood suggested:
One possible solution is to "unify" reputation in these cases so intentional self-answers (that is, answers that come in within 1 second of the question being posted) don't get rep for both the question and the answer, but just the answer. This would at least unify the incentives a bit and prevent the perception, correct or not, of double-dipping.
I was against it then and I'm against it now. Question and answer, whether posted by the same user or not, are two separate posts.
If somebody posts a horrible question with a brilliant answer, he deserves to lose rep for one and gain rep for the other. Likewise, if somebody writes a well-researched, clear and non-localized question and answers it himself, he deserves to get for both posts.
Artificially limiting the rep you can earn from it isn't consistent with the fact posting questions to answer them yourself is explicitly encouraged.