Can I install Drupal Commerce as a site in a multi-site architecture, preferably using Commerce Kickstart?
After much research, I've found out the following:

Can Commerce Kickstart be added to a multi-site installation?

The answer is No.

As Clive pointed out, CK ships with patches to Drupal core, so it's definitely not unmodified.  Additionally, CK will break if one tries to migrate an already existing, stand alone installation to be one of the sites in an existing multi site setup. CK depends on the installation profile to be present to continue to function correctly. Finally, Bojanz, a contributor to the project, points out, CK is a distribution and has to stand alone.

Can Drupal Commerce be added to a multi site installation?

The answer is Yes.

In that same answer above, Bojanz also points out that Drupal Commerce can be added to a multi site architecture. The caveat is that it has to be built out a la cart with modules as needed that make up the Commerce Kickstart distribution.