Emphatize text in ERC

erc-emph.el

(defun erc-emphatize ()
  (when (eq erc-interpret-controls-p t)
    (goto-char (point-min))
    (while (re-search-forward "\\(?:^\\|\\s-\\)\\*\\([^*]+\\)\\*\\(:?$\\|\\s-\\)" nil t)
      (replace-match "\C-b\\1\C-o" nil nil))
    (goto-char (point-min))
    (while (re-search-forward "\\(?:^\\|\\s-\\)_\\([^_]+\\)_\\(?:$\\|\\s-\\)" nil t)
      (replace-match "\C-_\\1\C-O" nil nil))
    (goto-char (point-min))
    (while (re-search-forward "\\(?:^\\|\\s-\\)/\\([^/]+\\)/\\(?:$\\|\\s-\\)" nil t)
      (replace-match "\C-V\\1\C-O" nil nil))))

(add-hook 'erc-send-pre-hook
          (lambda (string)
            (with-temp-buffer
              (insert string)
              (erc-emphatize)
              (setq str (buffer-substring (point-min) (point-max))))))

(add-hook 'erc-insert-modify-hook 'erc-emphatize)