Stranded is not code [NEC]. A good home inspector should catch it and
required it's replacement before getting an occupancy permit.

Can you cite where the NEC says this? I'm pretty new to this, so I
might be missing something, but I can find nothing.

A quick web serch leads me to believe that this is common enough
practice that it hardly warrants mention. The closest question that
comes up is whether it's OK to connect stranded wire directly to the
screw terminals on outlets. The nearly unanimous answer is that it is
code as long as the outlet is listed for it. All this discussion would
seem pretty pointless if you're not allowed to run stranded wire at
all...

Just for laughs I looked up the UL info on the outlets I've been using,
and the only thing it bothers to specify is that you MUST use 14 awg
solid for the slide in connectors on the back. For the screw termianls
it just says "up to No. 12 copper or copper clad wire"...

The closest thing I can find in the NEC is that 8 awg and LARGER run
through a conduit MUST be stranded. This does not imply the
contrapositive...