David,
For an announcement list, why would they want to go to the web site?
...
The issue is with getting them on the list in a smooth and simple
manner, and the website does not help with that.
If their tendency is already to use email rather than the web, you could reinforce that in the customizable portion of the invite.
I realize that's just side-stepping the issue you raise, but the best I can do is offer advice on how to use the site as it is.
That's a useful tip, but really it does not look good to be saying
"Ignore anything after this".
You don't have to say that. As long as your portion makes a complete statement of what they need to know and to do, they'll rather naturally ignore the rest.
Shal
Shal Farley