The stock market valuation of an obscure Hong Kong company has soared in recent days for no apparent reason. Last month, AMTD Digital debuted on the New York Stock Exchange at $7.80 per share. The firm’s shares have been on a rollercoaster ride this week, closing at $1,100 on Wednesday. Some analysts have compared AMTD Digital’s sudden growth in value to “meme stocks,” which garner appeal among individual investors through social media. The trading of the company’s shares has been especially tumultuous this week, as its market capitalization surpassed $300 billion on Tuesday. This means that AMTD Digital briefly surpassed...