Updating which specs have "pretty good" adoption

[Thomas Kluyver]

I'm working on updating the list of specifications here:
https://wiki.freedesktop.org/www/Specifications/

I think several of the specs listed as "not yet widely used" are now well accepted, and could be upgraded to "pretty good adoption". In particular, these specs describe files which are on my (Fedora+Gnome) system, and I'm pretty sure I've been seeing some of the files around for several years:

- Icon naming: https://specifications.freedesktop.org/icon-naming-spec/icon-naming-spec-latest.html
- MIME application associations: https://specifications.freedesktop.org/mime-apps-spec/latest/
- Sound themes: http://0pointer.de/public/sound-theme-spec.html
- Help: https://wiki.freedesktop.org/www/Specifications/help-spec/help-system-spec.xml
- Thumbnails: https://specifications.freedesktop.org/thumbnail-spec/thumbnail-spec-latest.html

Can anyone confirm which other desktops do or don't use each of those specifications? And if you know, what version of the desktop added support for them?

I'm hoping to find that all major desktops have supported these specs for a long time, which makes life easy. If that's not the case, we can figure out what counts as "pretty good" adoption.

Thanks,
Thomas