Just found this little gem regarding read-only buffers in Emacs:
A buffer visiting a write-protected file is normally read-only.
Here, the purpose is to inform the user that editing the buffer with the aim of saving it in the file may be futile or undesirable. The user who wants to change the buffer text despite this can do so after clearing the read-only flag with C-x C-q.
This is cool, because Perforce makes files read-only by default (to encourage you to open them before you edit them, though you can do this after the fact if you’re careful) and because I’ve been making the files for my web site read-only as a small measure to deter site defacement. I had been using vim for editing my web site files because
w! can write to read-only files, but now it looks like I have a convenient way to use Emacs as well.