Re: latex mode, nexted subscripts are unreadable

[karl@freefriends.org (Karl Berry)]

    I tried evaluating a modified defface definition  (in a temporary file,
    not by changing tex-mode.el) but this had no effect.

I believe that defface is like defvar et al; if the symbol is already
defined, it won't do anything.  You can call modify-face or
set-face-attribute from Elisp to change existing faces.
    
    $a_{b^c}$ makes $c$ elevated at the same level as the $c$ in $a^c$;
    the raising is done relative to $a$ rather than to $b$.
    Maybe this is a separate bug?

Maybe.  I believe this is the code in tex-mode.el that does the raising
and lowering.  I don't see any reason offhand for the different face to
affect it, but unfortunately I really can't say for sure.

(defun tex-font-lock-suscript (pos)
  (unless (or (memq (get-text-property pos 'face)
		    '(font-lock-constant-face font-lock-builtin-face
		      font-lock-comment-face tex-verbatim))
	      ;; Check for backslash quoting
	      (let ((odd nil)
		    (pos pos))
		(while (eq (char-before pos) ?\\)
		  (setq pos (1- pos) odd (not odd)))
		odd))
    (if (eq (char-after pos) ?_)
	'(face subscript display (raise -0.3))
      '(face superscript display (raise +0.3)))))

Sorry I can't help more.

Best,
Karl