jmn-erc-format-nick.el

;; Align messages in Emacs erc IRC-client by setting nick names
;; to use a fixed number of chars.

(defun jmn-erc-format-nick (&optional user channel-data)
  "Like `erc-format-nick' but trim/pad nick to a fixed length.
   - Based on xwl-erc-format-nick"
  (let ((nick (erc-format-nick user channel-data)))
    (when (> (length nick) 9)
      (setq nick (concat (substring nick 0 6)
                         ".."
                         (substring nick -1))))
    (when (< (length nick) 9)
      (setq nick (format "%-9s" nick)))
    nick))

;; Use with below (or customize):
(setq erc-format-nick-function 'jmn-erc-format-nick)