A lot of icon themes are pure garbage, or at least incomplete. I don't think the example chosen here is any worse than what I've seen on my own system. Honestly, most icon themes are a failure; visual metaphors are just plain hard, and there's no substitute for literacy.
For example, what happens when there's system searching element that needs to be in visual proximity to a magnification, zooming or loupe-inspection element? It's impossible to know if an icon theme is going to maintain consistency and/or disambiguity with the default theme.
Actually, "system-search" is always "The icon used for the “Search” item in the desktop's panel application.".[1] Admittedly that makes it a bad example because an application generally doesn't need this icon.
> For example, what happens when there's system searching element that needs to be in visual proximity to a magnification, zooming or loupe-inspection element?
Hopefully, the application uses the standard icons. The user might have difficulties distinguishing idiosyncratic, unfamiliar icons.
[1] https://standards.freedesktop.org/icon-naming-spec/icon-nami...
Freedesktop.org is kinda bad at showing that it isn't a dead organization.
The 0.8.90 is also wrong, since then there've been some changes - diff:
+ system-reboot The icon used for the “Reboot” item in the desktop's panel application.
+ user-available The icon used when a user on a chat network is available to initiate a conversation with.
- user-online The icon used when a user on a chat network is available to initiate a conversation with.
Why? There is already a standard. It does not specify what icons look like, but what they mean. Replacing an icon with another that has the same meaning is not a problem. Of course, if you, say, abuse the "system-search" icon to show a looking glass, this will not work with a theme using a different metaphor.
The icon theme displayed in the open letter is just garbage. Using it as an an example is like saying distributions should not change the default font because they might choose Wingdings.