I am using a Mac (OS X 10.4.10) and when I click on “Edit this person” it does not give me a “Delete” option. At the top right I see the vCard options but there is NO delete option. Just doesn’t show up. Any idea why this is happening??

I believe you are only able to delete contacts which you have entered. If another user has entered the contact you are trying to delete, then no, you will not get the option to delete.

I think you can only delete a contact that has been entered directly. Contacts I have entered through vCard import are only able to be deleted en masse. It appears that merge is also only available for contacts typed into the page, and not for imported contacts.

This seems a usability flaw to me – why wouldn’t all my contacts be treated the same? I shouldn’t have to remember how I entered a contact – and in any case, how do I delete or merge a contact that came in via vCard?

You can’t delete contacts other people entered (as they may be their contacts). You can delete any contact you entered or added. You can also delete previous mass imports:
http://37signals.blogs.com/products/2008/03/highrise-improv.html

How, though, do you delete individual contacts that you have added from a mass vCard import? I only want to delete some of the contacts I uploaded, not all of them.