Specifically this question "What is a Sangha? Do you have to be a Buddhist to join a Sangha?"
The Questioner seems to answer himself a few minutes after asking the question. I feel that this could lead to a conflict of interest in the integrity of this site.
Answering your own question is fine, and considered well within "best practices" as far as I know. The problem will more be in the content of the question or the answer. If the question is opinion-based, for example, or overly-broad, then it should be flagged, regardless, of course, of whether the questioner answers it themselves or not.
"Doing that is OK" is the normal SE policy.
But on this site I think that was overridden by the consensus/voting on this answer to the meta-topic titled, "May I share my research, by posting questions on this site and self-answering them?".
Sometimes, it will happen: when you don't know the answer, you post a question, nobody answers, you do the research, now you can answer your own question ... but (to avoid flooding the site with such topics) this shouldn't happen more often than maybe a couple of times per person per year.
