quoted

Does a hashmap guarantee an order?

No, it definitely doesn't.

I guess the reading-between-the-lines assumption that I didn't quite say
is: I think most (if not all) of the users of sorted string lists don't
actually care about a particular order. They just want efficient lookup.

quoted

I thought we had an example of an ordered list in the submodule code
but could not find it, maybe it is gone already or did not rely on the order
as I thought.

It turns out we make never use of a custom compare function in
the stringlist, which helps gaining confidence this use case is nowhere
to be found in the code.

Plenty of code uses the default strcmp. You can find users which assume
sorting by their use of string_list_insert() versus _append(). Or ones
that call string_list_sort(), of course.

Here comes my reading-between-the-lines assumption:

When using the default comparison function, you probably only care
about the efficient lookup as described above, but if you had a non-default
order, then we'd have strong evidence of the contrary as the author of such
code would have found reasons why that order is superior than default order
(and don't tell me a different order helps making lookups even more efficient,
this must be another reason).