https://forum.miata.net/vb/showthread.php?t=725007
TL;DR: Newbie (somehow) drops a ~pea-sizedchunk of porcelain from spark plug into cylinder, cannot tell if it was vacuumed out or not, and after even suggesting firing up the engine, some people tell him to go for it. WTF.
Some of the questions and answers make it apparent how little people know about engines, never mind materials.