> I "know" this but often forget. When I look through iMessage history at pictures I've sent and received, there are often stray bits of overheard conversation that the sender wouldn't necessarily want or intend to include.

I was surprised with this too. This should be really made more clear.

The Live Photo is not silent at all, in fact it is very loud with the noise of water and phone fiddling.

It wasn't silent for me, I could hear the wind.