Scenario:
When looking at Historical Timesheets, you get to see a disabled users timesheet in grey color font, but this functionality is not there when viewing the Timecards list.

Resolution:
This is by design that there is no difference in the way a Timecard is displayed on the Timecards screen. However, when you look at the Timecard Dashboard, you have the filter available that allows you to select users based on there status. This will allow us to look at data only for enabled users or only for disabled users.