Don Y wrote:
~1980 house is built of stucco over cinder block (in some places) and
slump block (in others).

There are long, narrow, noticeable cracks in the exterior stucco
suggesting some subsidence (water is all ground sourced, here). Neighbors
suggest "just slather some paint over it". frown

Is it OK to just patch these cracks? Or, should we expose the
underlying blocks to get an idea as to how much they've penetrated
the structural block?

If *just* superficial, any advantage to polymeric patches vs. (cement)
"stucco patch"?

And, if the cracks permeate the underlying block (presumably on mortar
lines), what's the recommended remedy? Anything "injectable"?
(fine mortar, cement adhesive, etc.)

Since the cracks are there because of movement, I would not use a
cementatious material to patch them. I want something that allows for a bit
of movement. I caulk and paint them. For hairline up to maybe 1/8 I use
acrylic caulk, I had a joint between a free standing wall and the house
that had opened up to 1/4 - 1/2, used polyurethane caulk.

The norm IME for stucco cracks is on block joint lines, easily visible. I
haven't worried about whether the cracks penetrate into the block joints as
there is nothing I could do to repair same without major effort and expense
and I view some joint cracks rather the same way as I would in wood; i.e.,
minor local damage does not impair the whole.