Jeremy Allaire, co-founder of cryptocurrency company Circle Internet Group Inc., saw his wealth soar to over $1.7 billion on Thursday as the company’s stock nearly tripled on its debut trading day.

Tether’s $515 billion valuation stirs IPO discussions, but CEO Paolo Ardoino rejects going public, focusing on private growth and stability.

Shares of Circle surged after its debut as a public company, but the crypto player may face headwinds if the Federal Reserve ...