Europe has finally emerged from its debt crisis with healthy economic growth, but it can’t shake one relic of its troubled times: negative interest rates.

The policy was tried by Sweden briefly in 2009 and 2010 but eventually was implemented by Denmark, the eurozone, Switzerland and Sweden again over the subsequent five years before landing in Japan two years ago. Negative rates—where the central bank charges commercial banks for money held at the central bank—helped safeguard economic recoveries by lowering borrowing costs...