In the Emacs Lisp documentation, I often come across quoted symbols like
`buffer-file-name' inside docstrings. The intersting thing here is the style of quoting, by surrounding the symbol name with a backtick and a quote. I was curious where this style came from. According to this answer it could be related to a limited character set.
Another thing to notice is that these quoted symbols have syntax highlighting in
emacs-lisp-mode, whereas symbols quoted with only single quotes, for example, 'buffer-file-name', does not get any syntax highlighting.
So this indicates that the backtick-quote syntax has to be a well-known convention in Emacs. But after googling the documentation, I could not find it mentioned anywhere. In the Emacs Lisp manual there is a section named "Tips for Documentation Strings"; it says
When a documentation string refers to a Lisp symbol, write it as it would be printed (which usually means in lower case), with single-quotes around it.
but it does not mention the style of quoting.
C-h f thing-at-point RET and then click the link to the source code to see some more examples of the quoting style:
(defun thing-at-point (thing &optional no-properties) "Return the
THING at point. THING should be a symbol specifying a type of
syntactic entity. Possibilities include `symbol', `list', `sexp',
`defun', `filename', `url', `email', `word', `sentence', `whitespace',
`line', `number', and `page'.
When the optional argument NO-PROPERTIES is non-nil, strip text
properties from the return value.
See the file `thingatpt.el' for documentation on how to define a
symbol as a valid THING."
So all this gives an indication that one should use the backtick-quote style to quote symbols, but is this style documented anywhere?