Thus 1.100 is "newer" than 1.99. Otherwise, a pure alphabetical sort would show (in order of oldest->newest) 1.100 1.2 1.250 1.30 1.550 1.90 1.99 Which is obviously wrong (or, at least, counter-intuitive). If you can point me in the right direction, perhaps I'll take a stab at this.
This is exactly what Portage does. This bug report doesn't list any specific bug, so I'm closing it.