Need a better way to create an optional comma-delimited list

Summary: For example, look at the AKA field in my Songbook Space. There isn't a great way in QL to say, "if this list/set is non-empty, show it with this boldfaced label and then the contents, comma-delimited".

Note that _section comes close, but doesn't really get there. In particular, it doesn't have any good way of expressing the _commas concept of putting commas between elements.

There is an abstraction trying to break out here, but I'm not quite sure what it is yet. But this use case is so common that there should be a one-stage function to do it.