In:

http://www.roundup-tracker.org/docs/customizing.html#special-form-variables

it is stated that:
===================
In the following, <bracketed> values are variable, “@” may be either ”:”
or “@”, and other text “required” is fixed.
[...]
Two special form values are supported for backwards compatibility:

@note
    This is equivalent to:
      @link@messages=msg-1
      msg-1@content=value
    except that in addition, the “author” and “date” properties of
    “msg-1” are set to the userid of the submitter, and the current
    time, respectively.
=======

If the user renames the message @note field to :note, the textarea
is not populated with the text from the "Make a copy" url created by
copy_url.

One idea I have to address this is to add an additional parameter
to copy_url(..., special_char='@', ...) that can be overridden
when called to use ":". It looks like only @note is affected
since the only other special variable is @template which is
interpreted by the roundup code and not used in a template.

Does this seem to be a reasonable way to handle it?

The only other way I can think of doing this is to copy the function
into the tracker and make the change in the copy then call the new
function from the templates. Blech.

Any other ideas, comments?

Also it just occurred to me, is the : or the @ form the preferred
form. I remember one of them is the legacy character, but I don't
remember which.