I am with @wbond, too. Partially splitting ligatures by selections causes unpredictable and hard to handle effects. In general I therefore find ST3148's behavior more consequent and consistent. If a series of chars is to be rendered as ligature, it must be under all circumstances or not at all.
I am wondering, whether it was possible somehow to (efficiently) return to the old rendering behavior in some way and just partially redraw the selected part of a ligature.
1. Draw background
2. Draw unselected ligature
3. Draw selection background
4. Draw selected part of ligature and clip it at selection background boundaries.
Clipping may be a bit tricky, but it could solve the foregroundColor issues for those who need them. I personally did not pay any attention to the way selections are rendered at all.
Jumping characters while selecting text is more annoying, I think.