When is "-" required in articulations?

[Trevor Daniels]

I'm drafting a section for the Notation Reference which says:

When adding articulations to notes the direction indicator,
@code{^}, @code{_} or @code{-}, can usually be omitted, in which
case @code{-} is assumed.  But a direction indicator is
@strong{always} required before

@itemize
@item @code{\tweak} commands and
@item @code{\markup} commands.
@end itemize

Can someone please confirm that this is correct and that there
are no more note articulations which _require_ a direction indicator.

TIA

Trevor