.ss paragraph-style-footnote example, then and now

[Dave Kemper]

Speaking of the .ss section of the Texinfo manual, I'd like to get feedback on 
a change made here -- in particular, an example that illustrates a somewhat 
novel use of .ss to insert discardable horizontal space between individual 
notes in a block of footnotes.

Commit 866bc203 
(http://git.savannah.gnu.org/cgit/groff.git/commit/?id=866bc203) changed this 
example.  The text introducing the example (taken from after the change, but 
applies equally to either version of the example) says:

    A related application of the 'ss' request is to insert discardable
    horizontal space; i.e., space that is discarded at a line break.  For
    example, some footnote styles collect the notes into a single paragraph
    with large spaces between each.

The example itself originally read:

    .ll 4.5i
    1.\ This is the first footnote.\c
    .ss 48
    .nop
    .ss 12
    2.\ This is the second footnote.

    RESULT:

    1. This is the first footnote.        2. This
    is the second footnote.

The new version of this example is:

    .ie n .ll 50n
    .el   .ll 2.75i
    .ss 12 48
    1. J. Fict. Ch. Soc. 6 (2020), 3\[en]14.
    2. Better known for other work.

    RESULT:

    1. J. Fict. Ch. Soc. 6 (2020), 3-14.     2. Better
    known for other work.

The new example really only demonstrates that you can set the sentence-space 
parameter of .ss to a large value to create a large space between sentences.  I 
don;t think this is particularly illuminating; one could easily deduce that 
from the description of .ss.  Its one bit of value-add is that it shows a use 
case -- separating footnotes -- that a user might not have otherwise thought of.

However, the original example shows this as well, but also has additional 
attributes that the new example lacks:

  - It shows how to use .ss to insert extra (discardable) horizontal space 
without overriding its normal use to also separate sentences.  That is, in the 
original example, one of the footnotes could have consisted of more than one 
sentence, and groff would use normal sentence spaces between sentences and 
extra-wide ones between footnotes.  (Arguably, the example could be expanded to 
demonstrate this explicitly, but I think it's fairly deducible from the example 
as written.)  The modified example does not have this property; any sentence 
breaks within a footnote would be given footnote-separating space.

  - It shows a use of the .nop request, whose description otherwise leaves 
users wondering what utility it has.

  - It shows that the second .ss parameter will take effect multiple times on 
the same output line.  This may not seem particularly noteworthy, but it turns 
out to not be true of all roff implementations: 
http://github.com/n-t-roff/heirloom-doctools/issues/103

The footnote text in the retooled example does look like real footnotes, but 
this improvement could be easily retained while restoring the functionality of 
the original.  In fact, the new footnote text could easily use sentence space 
within the footnotes, allowing the example to demonstrate word spaces, sentence 
space, and nonce footnote spaces within its two lines of output.

What do you think?