Inconsistent behaviour in menu item path

I've come across what I think is a bug in the way menu item paths are handled if they contain special characters like &. This issue was originally discussed in the forums here.

Basically, if a relative path containing an '&' is specified, the '&' is converted to '%26' when it is displayed and the link does not work. If the same path is specified in its absolute form, the '&' is left unchanged and the link works. ('?' and '=' are left unchanged.)

I came across this while using the CiviCRM module and I'll give an example using its links. However a quick test suggests that this issue applies to any links regardless of module, so it's not CiviCRM specific.

So, if I have a menu item path containing the following relative path:

  civicrm/contribute/transact?reset=1&id=1

it is output/displayed as:

  http://site.com/civicrm/contribute/transact?reset=1%26id=1

If I modify the menu item to use the following absolute path (by adding the site and leaving the rest unchanged):

  http://site.com/civicrm/contribute/transact?reset=1&id=1

it is output/displayed as:

  http://site.com/civicrm/contribute/transact?reset=1&id=1

The relative link fails when you click on it, while the absolute link works correctly. This would seem to be a bug.

(I've done a quick check under D6.0-RC2 and this bug does not appear.)