archvenison

But at the time of the Recreance the Radiants believed that they had actually won, so Odium wasn't there.

I don't think that the Recreance was caused by the Radiants making a conscious, logical decision to stop betray their ideals. Rather, the revelation that humans were originally the bad guys and had used their powers to destroy a different world, combined with Honour saying they would do it again (and perhaps whatever happened in Natanatan) caused them to lose conviction in the Ideals and thus act contrary to them. As we know from Kaladin in WoR this is enough to kill their spren. Also when Syl offered to leave Kaladin he had only sworn the first Ideal which I suspect is before the point of no return.

I vote for simply calling them glyphs (as they are called in the book) until we learn of another glyph system.

I've noticed two things that seem important: 1) Brandon has said that Roshar moves slowly westward due the high storms; 2) He has commented that Roshar's similarity to a highstorm is important. My theory is that in addition to moving west Roshar also slowly spins, causing the spiral shape. This is supported by fact that the continent is more circular when on a globe.