readmore not set

In CCK 5, we do not actually render both teaser and full page display on a node's view, so there's no way for us to do something like
the 'usual' :
$node->readmore = (strlen($node->teaser) < strlen($node->body));

I guess the right criterion would be 'if display settings are different for teaser and full page', but it looks hairy, plus I'm not even sure that makes sense... I think we're left with 'an always TRUE or always FALSE' choice ?

Re-categorizing this to a feature request.

I am trying to understand if this issue is the same as mine.

I have a content type with no body field (by setting body label to blank).
I then use a CCK text field (trimmed) for teaser and body data.
The end result is that there is no readmore link, since it looks like node.module is assuming it is the only one creating the teaser. The proposed fix or patch do not work for me (not sure why, still checking).

Also the patch is for cck 5.x, so it does not apply anymore. More on the patch, 'hidden' is not the only thing to check. The right thing would be to compare teaser formatter to full formatter.