What’s the deal with the “soaping effect” or those white streaks from emulsions?

Rather than break this into a number of posts over the course of a few days, I decided to leave this as one giant post for easier reference. Honestly, I didn’t expect this to reach over 3,000 words, but here we are!  What causes the “soaping effect” or “an undesired foaming phenomenon observed in skin creams…