I had a nice surprise discovery today.  If two people get an approval request and one approves it, when the other clicks the approval link in their email they end up on a "Data not available" page.  This makes the user think something is broken vs. just letting them know the record is already approved.

Consider upvoting this idea to get this corrected:

https://success.salesforce.com/ideaView?id=08730000000XnlbAAC

@Solo Admins @Admin Group, Raleigh, US @* Salesforce Administrators * @MVP Office Hours (US) @Salesforce Flow Automation