It's called the median.

Geez, what next?
"In every thread, somebody must post"
"In every thread, somebody must troll"
"In every thread, somebody must be second"
"In every thread, somebody must be the penultimate poster"
"In every thread, somebody must offer an objectional viewpoint merely to start an argument"
"In every thread, somebody must call something "rubbish""
"In every thread, somebody must mildly dislike something"
"In every thread, somebody must feel very strongly on a certain point, only to discover that others have already said it, and end up posting "me too""
"In every thread, somebody must point out how repetitive this is"

Hey, this is fun!