There is a feature in Modo called 'Select Through' that is enabled
by default, so that if you're in Item mode, select an object,
transform it, then click on another object, you're still in whatever
transform tool you were in, but your selection has changed. Just
keeps you from having to drop and reactivate the tool you were
using. Now the transform tools themselves don't require you to be
interacting with an actual handle, so in the case of the Move tool,
you could very well click off somewhere in the viewport and move the
item. But if a different item is under your cursor when you click,
it will select that item instead.
You can disable this if you like by going to the Lists tab (3 over
from Properties, along the right), then in the Pipeline section,
with your tool active, right click on the tool's entry in the
Pipeline view and uncheck 'Select Through'.
Not sure if that's what you're looking for?
-Tim