The typographical symbol dagger (†) has several meanings. Possibly its most common use is as a footnote marker.

According to You Have a Point There: A Guide to Punctuation and Its Allies (Partridge, 1953), when it is used for this purpose, it must be used for second footnotes only; the first footnote should be indicated by an asterisk (*), the third a double dagger (‡) and further footnotes other symbols or numbers.

Where does Patridge's rule fall on a scale of one to ten, where one is "this is just one guy's random opinion" and ten is "this is a widely accepted rule of English and any deviation from it is unarguably incorrect"?

This question was inspired by this Meta Stack Overflow question about the use of daggers on Stack Exchange site FAQ pages.