darrenSP - You can easily update the confirmation message from a text editor. 

Below is the text key used for show Thanks for your feedback message. 

page.RatingEnumerationDisplay.feedback.success.title

Studio -> Text Editor -> Community Text 

Lithium uses the text key for each string appearing in the community.  You can search for the string you want to update from there. 

https://community.lithium.com/t5/FAQs-email-templates-and-text/About-text-keys/ta-p/109029

https://community.lithium.com/t5/FAQs-email-templates-and-text/Find-text-keys/ta-p/109027

Regarding the custom component for this, there is no POST API call available for helpfulness, you can only perform GET action. 

https://community.lithium.com/t5/Developer-Documentation/bd-p/dev-doc-portal?section=commv2&collection=tkb_helpfulness_ratings#constraints-message.id

My apologies.

You'll need to reference the results as so:

<#if activity.results.name.UserUpdated??>
  ...
</#if>

 Sorry for the confusion!

When an SSO cookie is processed, Lithium tries to delete the cookie and replace it with a cookie that starts with an exclamation point (!lithiumSSO:).  This is to prevent the app from trying to process the same cookie it's already processed more than 1 time, which we don't allow (for security reasons).  We also put time limits on how long an SSO token is good for, so it's best practice to only set an SSO cookie right befor sending a browser to the community.  

It shouldn't matter how you generate the cookie (server-side or ajax call), as long as the request is secure and cannot be used to get an sso token that lets you log in as another user.  

If you are making an ajax call to another domain to get an sso cookie, make sure you have CORS configured correctly for that community and are sending the correct headers.  

If an sso cookie is set by an ajax call, you should always reload the page (or make another ajax request with the sso cookie) since the sso processing happens on the server-side.

I googled "ajax can't set cookie firefox" and found this stackoverflow article:

Jquery Ajax Firefox not sending cookie (Chrome works)

Maybe what you're trying is related?

-Doug