Since asking this question and answering it myself (having read Jeff Atwood's take on this on mSO), I've done a little more reading and realized it is somewhat controversial.
I guess each community decides for itself how it feels about this practice. How do we feel about it here on dba.se?
Do we prefer people
- not to ask/answer questions they already know an answer to
- to wait a certain period (1h?, 1d?, more?) before answering
- to answer immediately to save others the trouble of re-doing your research
- to use the CW flag (on question or answer or both)
-----edit
There is a new feature that allows a question and answer to be submitted at the same time - making it all the more obvious that self-answering is acceptable and even to be encouraged