Exclamation points (!)
Even rarer than question marks, exclamation points are almost never used in academic or formal writing. They owe their rarity in academic writing to the spirit of dispassionate discussion that formal writing usually requires.
The excitability communicated by an exclamation disqualifies the exclamation mark from acceptable use.
The importance of some fact should be obvious enough when stated, which means it should not need to be exclaimed. The exclamation point in academic writing is a bit like the shout in polite conversation.