Why does the carat (i.e. ^ ) character sometimes not appear in an answer, even when it shows up in preview?

In my answer to the question at https://www.fluther.com/225899/why-does-1kg-squared-1kg-while-1000-grams-squared-higher/#quip3712026 I tried to indicate “grams squared” as g^{2. That is a g, followed by a carat character (} ) followed by a 2. (Well, it fails here too – showing up in preview, but not in the posted question Details.) I wrote this consistently, and it appeared consistently in the preview, but after saving the answer, the answer itself shows just g2 (and kg2) on the last line, but shows it correctly on the lines above that. What on earth is going on, and is there a way around it?