The Short Version
EU law directly prohibits this practice. Directive 2009/110/EC (EMD2) requires electronic money institutions to safeguard client funds and explicitly bars investing those funds in securities for profit-sharing purposes. ECB accounting guidance further confirms that unrealized mark-to-market gains are recorded under revaluation accounts and are not recognized as distributable profit. No authoritative source supports the existence of any compliant structure permitting an EMI to distribute unrealized bond portfolio appreciation to clients.