How high is this ice wall meant to be?
Concorde flies (or flew at least) at around 55,000 feet, meaning the atmostphere reaches at least that high (in the FAQ it's stated that aircraft fly due to the accepted idea of lift-due-to-differential-air-pressures). If a flat earth was accelerating constantly the atmosphere would spill over the edges unless there was something to keep it in. The height of concorde flights means these cliffs would have to be a minimum of 55000 feet (that's over 10 miles) high. You'd see them, especially with line-of-sight to everywhere, since you've decided there's no curvature.