Unfortunately I either don't understand or can't recreate this issue on Chrome in MacOS X either locally or on http://esmecloudserverapache.dickhirsch.staxapps.net. I do the following:
1. Create a new pool (in Chrome)
2. In a different browser (Safari) I create a new user (testuser2)
3. (Back in Chrome, for the duration) reload the My Pools page
4. Choose the new pool
5. Click the edit button
6. In the user field, type "test"
7. The "testuser2" value shows up in the selection list, and I select it
8. Add the user to the pool with Read capability
9. A couple of seconds later the list of users in the pool is automatically updated with "testuser2" and a "Read" privilege.
Are you doing step 3, reloading? This is necessary to get the name of the new user. The list of users is cached, I believe in the Snippet after the first attempt to add a user to a pool.