Well, we have to make a compromise. The PDF document has a small line
width, and you can't scroll horizontally...
Theoretically, the snippet could be printed with a smaller font size,
but this doesn't look very pretty IMHO. I consider the `\oo`
shorthand both innocuous and simple enough for a snippet.
My preference is the one that you said is inappropriate:
\once \override
Very.Long.Grob.PropertyToBeChanged = foo
If we introduce oo, then that adds extra lines to the snippet, and
it confuses the override (which is the purpose of the snippet) with
the convenience function (which is not necessary for the operation
of the snippet).
If you have to split 20 very long `\once\override` line this way, it's
(a) very hard to read, and (b) much longer than the few lines
introducing the little function.
I think that the benefit of the improvement in the typography is
outweighed by the increased difficulty of understanding the snippet.
I disagree. There are snippets with *extremely* sophisticated Scheme
code. What I'm going to introduce is very basic.