Process for removing an account from Gainsight?

That should do it, Jeff. You'll also want to be careful with any dependencies (CTAs, scorecard data, etc.) tied to that account. Also, you'll need to open a support ticket to delete that same record(s) from the Company object in the MDA.

If you don't want the account to be searchable anymore, you could just change the status (Edit Summary button) to "Inactive."  The data will still exist in the Customer Info object, but you can't hit that page.

Jeff, I have a process by which the customer is churned but I keep it in Gainsight. For those that have been loaded by mistake (they were flagged as customer and then switched to something else in Salesforce) I do delete the Customer Info object. The problem comes if it is a customer that we have loaded data on it. Because of the limitations on re-associating objects (like re-associate all the timeline activities or scorecard or success plans) you will have to make the call if you want to delete that account or not. If you do, you will probably need to remove all the different objects associated to the account before the customer info is removed.

With the July 2018 Gainsight release we will now offer the capability to delete customer records from the Gainsight Data Management screen. 

Watch this category for updates and release notes: https://community.gainsight.com/gainsight/categories/gainsight_release_notes

and 

https://support.gainsight.com/Release_Notes

Marcelo - can you elaborate on the limitations of re-associating objects?  I wasn't aware of any limitations.

So for example, lets say we have a success plan associated to a relationship object. That relationship object for some reason has to go and you want to move the success plan over to other relationship or to the account object. It seems like it is impossible to do it.