Where's the aether? (Spoilers)

[Jeeqbit]

there doesn't seem to be much of a difference between the Source and the reflections.

This does bother me to a degree. Why aren't people on the First smaller? Why is there not a clarification that using magic is harder for them due to lack of aether?

You'd think, the Source having been rejoined seven times, the denizens and worlds of Norvrandt, the Void, and Alexandria would be as faded to us

The Void can be explained by the joining of beings merging together. Alexandria can be explained because its people originated from The Source. But Norvrandt can't be explained so much unless they at least struggle with magic and summoning.

the aether from Rejoinings isn't going into the people of the Source or its new life

I think it's supposed to be going into people on the Source. Krile even questioned at first why her aether wasn't weaker after learning she was from a shard.

[TBerry]

This does bother me to a degree. Why aren't people on the First smaller? Why is there not a clarification that using magic is harder for them due to lack of aether?

If you split STEPHENSON 2-18 into 13 evenly massed stars, chances are they are still bigger and more massive than our sun. Probably even enough mass to create 13 black holes.
It's probably enough aether to not make any difference at all.