Biscriptalism on Starbucks cups, part 2

In "Impromptu biscriptalism on a Starbucks cup" (9/8/17), we encountered a Starbucks cup from Shenyang, northeast China that had the following handwritten notation on the side:  wài's 外's ("foreigner's").  I referred to the "'s" as impromptu because I thought that it was essentially a one-off phenomenon.  Nonetheless, I considered the "'s" to be linguistically significant […]