Anyway, I saw several responses talking about "properly soldered"
splices. Which, for me, begs the question what is a properly soldered
joint and how do you do it? Once again, thanks for all the input.

It's one where the solder wets and adheres to the metal, as opposed to just
sticking to its surface.

If the solder looks like a water drop on a waxed car -- with very sharp
boundaries as if the metal were repelling it -- then either it wasn't heated
adequately or the copper wire wasn't clean. The solder should flow freely
onto the metal and start to become alloyed with it.