Aside from the faith-based belief that there exists a soul, is there any good reason to suppose that a soul does in fact exist? [Spirituality & Religion]

It depends how you define "Good reason." Dualism, the philosophical position that there is more than just matter, is often invoked to support arguments for the soul. It's a defensible position (meaning that it's worth investigating) but ultimately, the truth of it is unsupported.

TLDR: There are arguments for the existence of the soul, but they're all pretty bad.