Every page on
Wikipedia a MediaWiki install to a root path outputs headers similar to the following:
<link rel="apple-touch-icon" href="http://en.wikipedia.org/apple-touch-icon.png" />
<link rel="shortcut icon" href="/favicon.ico" />
These headers are unnecessary because (in this case) the locations are the default location for the files concerned. They will be checked anyway by user-agents that make use of such files, so pointing to them is a waste of space (137 bytes uncompressed, ~28 bytes gzipped; about 0.2% of the page, but a more significant portion of the <head>).
Shortcut icon reference:
Before these links are output, the rendering code should check that they do not match the defaults, perhaps by expanding them with wfExpandUrl and comparing the two. If so, it should not output the links. (The documentation for these variables should be updated to indicate this feature.)
The protocol and host name of the apple-touch-icon also appears unnecessary; a relative path should be sufficient to specify a path on the current server. If that is removed too, it's worth testing setting an iPhone bookmark with a https: URL, just to ensure it still works.