Si si, era scontato che lo facessi. Mi sono dilungato per rispondere alla tua domanda.

Comunque ho trovato questo:

The text of the web page has to "qualify" to enable the Reader button. One criteria used for this is how long the article flows (how much scrolling is required to read the entire article.) So if you don't see the Reader button try this tip. Resize the Safari window width. As you drag the window narrower, the Reader button will usually display as some point. I discovered this after viewing the same web page on two different Macs (both Safari 5). One displayed Reader, and one did not. After sizing the windows equally, they both display Reader now. Hope this helps.
che non mi soddisfa appieno ma che è in parte vero.