Perhaps this is but my first impression of DBA, but it's surely a pleasant one.
I recently asked a fairly basic question about Postgres's indexing abilities. I was greeted with AMAZINGLY cordial and thoughtful answers, that not only addressed my question, but did so without making me feel like a gibbering idiot. Further, the respondents didn't hate-comment each others' answers, and even the less-than-helpful response was very professional.
How has dba.stackexchange cultivated such a professional, welcoming environment?