I don't use sieve scripts, but I noticed a minor nit in your patch:

Eric Abrahamsen <eric@ericabrahamsen.net> writes:

> @@ -215,6 +214,7 @@ sieve-edit-script
>      (sieve-mode)
>      (setq sieve-buffer-script-name name)
>      (goto-char (point-min))
> +    (set-buffer-modified-p nil)
>      (message
>       (substitute-command-keys
>        "Press \\[sieve-upload] to upload script to server."))))

[...]

> @@ -350,11 +350,13 @@ sieve-upload
>        (with-current-buffer (get-buffer sieve-buffer)
>  	(setq err (sieve-manage-putscript
>                     (or name sieve-buffer-script-name (buffer-name))
> -                   script sieve-manage-buffer))
> -	(if (sieve-manage-ok-p err)
> -	    (message (substitute-command-keys
> -		      "Sieve upload done.  Use \\[sieve-manage] to manage scripts."))
> -	  (message "Sieve upload failed: %s" (nth 2 err)))))))
> +                   script sieve-manage-buffer)))
> +      (if (sieve-manage-ok-p err)
> +          (progn
> +            (message (substitute-command-keys
> +                      "Sieve upload done.  Use \\[sieve-manage] to manage scripts."))
> +            (set-buffer-modified-p nil))
> +        (message "Sieve upload failed: %s" (nth 2 err))))))

In both hunks, 'message' is given an arbitrary string as its first
argument.  Any objections to the following cleanup of sieve.el text
formatting code?