The infinite earth plane leads to the question "why can nobody travel further than 90 degrees south (or north if you adhere to the SCM)?" Which they do not ever answer, (apart from one guy syaing "theres a wall in the way".) 
What do you mean by '90 degrees south'? I stand by what I said: with sufficient resources you or I could travel beyond the ice wall indefinitely.
Sentence in red verifies my view that they will rather toss in chaff than address the problem. Sentence in green is something that would already have happened if the icewall existed.
Let me put it this way: if the earth is flat, and if the icewall exists, it is either at the 90 degree south position, or it is not.
If it IS at that latitude, why is it not at the south pole?
If it is NOT at that latitude it is either nearer the equator or further from it. If it is nearer the equator, then people must be able to pass over it easily to reach the south pole, which leads to the question
why can nobody go even further south than that?If it is further from the equator then it does not require humans to have traversed over it, but will still lead to the question
why can nobody still go further south than the south pole if the wall is even further south?Wherever you want to put the wall, it leads to conflict with observed human activity.