Google-groups – How to remove someone from a Google Group without them being notified

As a workaround, can they sign up with a different email address, and then once accepted re-configure their account to use the desired email?

The group description is not viewable in the group landing page. It's viewable in the about page but it's only viewable to the members of the group who are able to see the topics.

The description could be viewable by the public in the Google Groups directory. In order to enable this the group owner should follow the below instructions.

From List a group in the Google Groups directory - Google Groups Help

The Google Groups directory is a browsable listing of all Google groups. To list your group in the Google Groups directory:

1. From the Topics screen, click on the Manage button. A list of items appears on the left-hand side of the screen.
2. Click on Information. Several items are listed.
3. Click on Directory. The group directory screen appears.
4. Click "List this group in the Groups directory."
5. (optional) Click Select a directory listing. A few directory listings appear.
6. (optional) Click on a directory listing, such as "Knowledge area." A few categories within the directory listing are listed.
7. (optional) Click on a category, such as "Computers." A few sub-categories appear.
8. (optional) Click on a sub-category, such as "Graphics." Your group is now categorized within the "Graphics" section of the directory.
9. Click the Save button. Your settings are saved and your Group will appear in the Google Groups directory (accessed when you click on the Browse All button from the Home screen.

Note: This setting doesn't affect whether your group's posts appear in search results. Refer to Controlling visibility of the group posts for further information.