What does the # mean?

In this document # is used to enclose strings of letters and words when they are being treated as symbols.

For example, if the word "banana" is under discussion as a symbol (rather than as an English noun), it will be shown like this: #banana#.

The need for a way to discriminate between words as parts of the English language and words as semiotic signs arises because the discussion about signs is taking place in English. It is difficult to use words to discuss the use of words.