> Oh yes, `\ \ \ \ ` would be pretty good. (My brain thought they'd be
> concatenated for some reason and I didn't try it. Distracted by other work,
> I suppose.)

They're actually lost nowhere (e.g., not even after unfinished f-expansion)

> I'm probably happy to leave things as they are for now. In fact, any sort of
> "indent" function would be better if it respected the line-wrapping routine
> and that's more work than it's worth right now. I'll table this thought in
> the Github wiki.

Do you mean \msg_indent:n {<text to indent that may be line-wrapped>} ?

Bruno