Edge wrote:

I recently remodeled a room that included hanging drywall. I used
lightweight joint compound and did the normal things such as taping,
applying compound, and sanding. I put on two coats of quality paint.
The results looked good when it was dry. However when seen with side
light you can see the textural differences in the joints between the
sanded joint compound and the drywall. The sanded compound looked
smooth while the drywall field looked rougher.

Although it is really no more than an annoyance how do you fix this?
Is there a coating like Kilz that can blend the two different
textures? What about a skim coat? Should I have used the lightweight
joint compound originally - is the sanded surface of the lightweight
too fine?

You need a drywall primer that specifically says it "equalizes porosity"
- otherwise you have to skim coat everything.