There has been some confusation as to if Lilypond questions belong here. For example, On which site are LilyPond questions on-topic? Could we clarify in the help center that these questions are perfectly on-topic here?
I like the generic "usage of specific music software" rather than calling out Lilypond,which would require calling out other similar (Finale, Sibelius) and dissimilar (maybe Rosegarden, Abelton Live*) software. This can be easily interpreted as an a priori limit on what software is valid to be discussed here.
I'm under the impression that the intent of this site that that which questions are "perfectly on-topic" is supposed to grow organically. Thus we don't want an explicit white-list, or black-list for that matter.
*I'm just throwing out examples of music related software; I'm not trying to make any comment regarding which software discussions properly belong here or elsewhere.