Hi
The issue referred to in your link was actually resolved in SP1 for 9.0.
Since you are using SP2, you should not be required to change anything in adminui.
Did you mark your variable as "input"?
If you do this, then you should see and Inputs/Outputs tab on the email startpoint.
If you then add %SUBJECT% in your Input data filter, this should not require you to do anything else.
Once deployed, if you then look in the adminui, this input should appear as Variable not literal.
Diana