The definitive word back from MSI in Taiwan is that the plastic piece covering that vent is there by design for the MS-1036. The access door on the MS-1036 is also used on the MS-1035 and MS-1047 for which the vents should be open.
Apparently, in the MS-1036, the plastic piece is applied to promote better airflow WITHIN the rest of the chassis which reduces the temperature of the palmrest. The heat reduction is only supposedly on the magnitude of 3 degrees celsius, so, in my opinion (one that is shared with one of MSI technical consultants in the US), the plastic piece should be left on if you are not experiencing CPU overheating. Should the CPU overheat, however, removing the plastic vent cover will reduce your temps. Chances are, this is advisable if you have configured with an Turion ML as is the case with Sleepydidge.