According to the Canon white paper on this camera, this camera's
sensor is fronted by a dichroic filter.  This implies the filtering
coating is on the front of the sensor's coverglass.  If this is the
case, the coating on the glass could be softer than normal glass.
Much of the dust we have in the air is quartz, which is much harder
than regular glass and harder still than any optical coating.
Cleaning it should be a process of removing as much dust as possible
with air pressure rather than initially using a swab initially which
could "drag" dust particles across the surface, sleeking or scratching
the coating.  It's not clear whether the coating is on the outside
or inside of the glass cover.  However, some kind of anti-reflection
coating is likely on the outside of the cover if the dichroic coating
is on the backside and even anti-reflection coatings must be treated
more carefully than glass.  
The process should be what it is with all precision optics;
1.  Blow off as much particulate matter as possible.
2.  Use a soft brush to carefully remove any adhering via static
charges.
3.  Use a cleaning solution and a swab as a last resort.  

Also, material that makes it way onto the coating other than dry dust
(organic particles, whatever) can contain an acidic component that
can permanently etch or degrade coatings.  That should be removed
immediately.
--Rich