BRUSSELS—The European Commission opened a debate on Tuesday on how to reform the European Union’s fiscal rules to deal with a pandemic-induced surge in public debt. “We are relaunching this review of our economic governance against a backdrop of enormous investment needs,” European Economic Commissioner Paolo Gentiloni said. “At the same time, the powerful fiscal support provided during the pandemic has led to higher debt levels. These challenges make it all the more essential to have a transparent and effective fiscal framework,” he said. The debate is to produce a fourth reform of the rules since they were established in 1997 to limit government borrowing to safeguard the value of the EU’s currency—the euro. Revised in 2005, 2011, and 2013, the so-called Stability and Growth Pact is now so complex that few people fully understand it. High public debt is the main headache now because public support to European economies …