The most recurring objection in the Reddit thread was: if most the hash power doesn't set the exact same limit, then there exists a "sweet spot"-block size that splits the network exactly in half.  I don't think this will happen because everyone knows that it could happen unless most people come to consensus on a limit.  As long as nodes/miners can efficiently communicate block size limit negotiations, then I think we'll witness what I call "spontaneous consensus" events…sort of like a phase change in matter (liquid -> solid) but instead the 1 MB limit crumbles and a new precise limit at (e.g.) 8 MB is erected.