Discussed internally. The reason it was never implemented: "stacking check takes up more performance than rendering the items" - might be discussable, but not here.

Reopened. While this may be a missing feature, the lack of it is causing several bad effects.

It seems that this one is closely tied with MCPE-13891.

Hello? Ghost town?

This may have to get fixed. In 0.15 the items laying on the ground cause even more lags for unknown reasons. Destroying a chest with many different items is still okay, because the items drop as stacked variants (1 entity, 1 stack of blocks.)
But when you build (as example a house) and break blocks, always 1 entity with 1 item, and they don't group to the stacked variants.

In MC:PC you can drop several items of the same type on the ground and it results in 1 entity with several items.
(If you dont get the point i can make a video.)

Heres what i mean. You throw a whole stack (or just 2 items) same time (Drop key alias "Q" + Shift, or open inventory, click stack, click outside of inventory), they create a stacked item.
but clicking "Q" will throw 1 item the time, when multiple are on the ground, they won't create such "stacked items"
(see attached file)

This can not be resolved.. They do not stack

I mean:
You throw a stack of Logs out of the inventory (while having menu opened, then click the itemstack, and click outside of the inventory again), and they create a itemstackentity.
(3 logs that are rotating around the middle one)
when you just throw one by one out (via drop key or out of the inventory) it will never stack. there are only itementities for every item you threw. (multiple logs, rotating around the same place)

If I understand correctly, you mean: if I drop a stack of 6 torches, then drop a stack of 6 more torches on top of them, you'd like to see the two items combined into one item that is a stack of 12 torches. If that's correct, then this isn't a feature that's implemented in 0.13.0.