He only tried to mimic the other's movements in jest.
For want of evidence, he was acquitted and allowed to resume his professorial duties; but it was forbidden to utter the name of the academy even in jest.
Rabelais is, in short, if he be read without prejudice, a humorist pure and simple, feeling often in earnest, thinking almost always in jest.
Camille Desmoulins, in jest and mockery, said of Saint-Just - the youth with the beautiful countenance and the long fair locks- "He carries his head like a Holy Sacrament."
The penny-post is, commonly, an institution through which you seriously offer a man that penny for his thoughts which is so often safely offered in jest.
Jacob is normally a kind person, so I think his rude comment was simply made in jest and meant to be funny.