Experts Exchange
OK, so after more and more of my Google searches turned up possible answers from Experts Exchange, I signed up for the free 7 day-trial, and extended it afterwards with the 1 month subscription plan.
This is a paid service, where premium members can post their questions (grouped into dozens of dozens of categories or “zones”), and experts on the related topic try to answer them. A new question opens a thread were question author and experts can post comments, possible solutions, clarifations etc., until the question author is happy and awards points for the answers.
Questions and answers relevant to others can be moved into the “knowledgebase”.
So far, my results are mixed – I received helpful response on one question about how to implement a profanity filter very quickly, but none on another question dealing with survey tools like LimeSurvey.