Because he’s asking about people who only read the open thread. Here he could get response from the people who do read LW in general, inclusive of the open thread, and people who read only the open thread (he’ll miss the people who don’t read the open thread). Outside the open thread, he gets no response at all from people who only read the open thread.
There would be far more selection bias if he asked about it outside an open thread, though.
Really? Why?
Because he’s asking about people who only read the open thread. Here he could get response from the people who do read LW in general, inclusive of the open thread, and people who read only the open thread (he’ll miss the people who don’t read the open thread). Outside the open thread, he gets no response at all from people who only read the open thread.
I see what you mean.