As unhappy as I was as a user of MetaFilter, this is a bad characterization. "Read the room," as practiced on MF, means that you can't storm into a thread with your guns blazing and make it all about you and your viewpoint by responding to everyone else in the thread and dominate by sheer volume of comments. Make your viewpoint known, but don't keep insisting that it deserves a response from others. Basically, don't be the asshole party guest who barges in and demands to be the center of attention. Compared to the rest of the internet, that is the mildest imaginable social norm.