Tooltips aren't always used. A further complication is that people tend to copyright icons, so the icons from one app to the next are substantially different.
> x for delete
I've seen 'x', 'delete', 'del', and the trash can. 'x' is also used to cancel or close. There's little consistency.
Well, those would be bad interfaces. But the standard in OS X and Windows apps is to have tooltips.
>A further complication is that people tend to copyright icons, so the icons from one app to the next are substantially different.
Is that a thing? They might not be able to show the exact same design, but they'd still be able to show a floppy disk or trash can or whatever.
That said, OSes could (and some do) provide standard sets of icons to be used across apps, and only special app-specific actions should have custom icons.
Some people have implemented icons poorly, so we shouldn't use icons, isn't a compelling argument. Those people might implement anything badly, for instance choosing bad text in a text-based approach.
Agreed re: consistency -- good icon design requires understanding what people expect and matching it, which isn't always easy (as the referenced project demonstrates!)
> x for delete
I've seen 'x', 'delete', 'del', and the trash can. 'x' is also used to cancel or close. There's little consistency.