Hi Mark,

While I have never seen the ¬ character before, I was even more surprised
that that was set as a notation for 'not'. With this commit (
http://git.savannah.gnu.org/cgit/emacs.git/commit/?id=bdda4855c635ecf4135e23321bdba023e9ae65c9
),
now all instances of not are replaced with ¬ in lisp-mode if symbol
prettification is enabled.

It seems a bit intrusive because I have never seen that notation before.
While I do know the sqrt notation √, I can imagine this being a source of
confusion/annoyance for some people.

Should these notations be instead suggested in the doc-string
of lisp-prettify-symbols-alist? People interested to see these notations
can then add that to their personal configs.

What do you think?
-- 

-- 
Kaushal Modi