But both of these are "work-arounds" for something which is actually
fairly normal musical notation. They are work-arounds because one
method implies that a note is not really the length that it appears to
be, and the other method implies that the dynamics actually belong to
another, silent voice. Neither of these is true in reality.
Ideally one shouldn't have to use trial and error, varying the length of
the second invisible rest, to get an acceptable appearance. We know
exactly where the final dynamic should go: it should be immediately
before the bar-line.
Perhaps at some stage the Lilypond developers could look at the
possibility of having a method of adding a dynamic (or text) for cases
like this, so that it is automatically right-aligned to a note or rest.
Additionally, if the note or rest comes immediately after a barline,
then the dynamic/text should be right-aligned to the barline itself. I
would suggest that a suitable input method would be to use a slash (/)
instead of or as well as the usual backslash (\).
I am not criticising Lilypond, which is magnificent. But it does seem
unfortunate that at the moment there is no way of directly inputting a
perfectly normal, if not particularly common, bit of standard notation.