Elon Musk's 'Use Signal' post spurred massive rally for the wrong one

A two-word app recommendation from Elon Musk has turned into a massive rally in the shares of a tiny medical device company in another case of mistaken identity.
 
"Use Signal," the Tesla CEO wrote on Twitter on January 7, apparently referring to the encrypted messaging service. By the end of the day, Signal Advance shares had surged more than sixfold.
 
That was enough to push Signal's rally over 5,100% in three trading days.