This piece of code is an extension to WikiMode. It sets the ispell dictionary automatically based on the language returned by the GuessBufferLanguage code.

First, we need to match a language returned by the GuessBufferLanguage code with an ispell dictionary. We define a table to match the languages with the dictionaries (note that I use a non-standard Swiss dictionary for German texts), and we add a new funtion to the hook for switching WikiMode on.

    (defvar guess-language-dictionaries
      '(("fr" . "francais")
        ("en" . "english")
        ("de" . "swiss"))
      "Alist of rules to determine the ispell dictionary for a language.
    Each rule has the form (CODE . DICTIONARY) where CODE is a string to
    identify the language (probably according to ISO 639), and DICTIONARY is
    the name of an ispell dictionary that can be passed to

    (defun my-wiki-change-ispell-dictionary ()
      "Call `ispell-change-dictionary' with buffer language.
    The buffer language is guessed by `guess-buffer-language'."
      (let ((language (cdr (assoc (guess-buffer-language)
        (if (null language)
            (message "Language unknown, ispell dictionary unchanged")
          (message "Guessing language: %s" language)
          (ispell-change-dictionary language))))

    (add-hook 'wiki-mode-on-hook 'my-wiki-change-ispell-dictionary)

Now we need to tell ispell that wiki names must be skipped. This is a little bit difficult since our regexp requires case sensitive matching. That’s why I had to advise ispell-region. When used while WikiMode is active, case-fold-search is set to nil. Up to now, I haven’t found any problems with that. It is a dirty hack, however.

    (defun my-wiki-ispell-skip-setup ()
      "Modify ispell to exclude wiki names.
    We do that by locally setting `ispell-skip-region-alists'.
    This will only work if some advice is given to ispell-region in
    order to do all skipping with `case-fold-search'."
      (make-local-variable 'ispell-skip-region-alists)
      (add-to-list 'ispell-skip-region-alist (list wiki-name-regexp)))

    (add-hook 'wiki-mode-on-hook 'my-wiki-ispell-skip-setup)

    (defadvice ispell-region (around ispell-case-fold activate)
      "When variable `wiki-mode' is non-nil, `case-fold-search' will be
    bound to nil."
      (let ((case-fold-search case-fold-search))
        (when wiki-mode
          (setq case-fold-search nil))