Hi Bruno, yes layers are slightly different in MoI, it's a little more flexible where you can work with sets of objects either by using object names or styles in combination with each other.

It's not really that named objects filter differently than styles, they just work the same way as styles where you can use them to hide/show/lock/select a batch of objects in one action using the Scene Browser.

You can install a plug-in to make it easier to assign to an existing object name, you can find that here:
http://moi3d.com/forum/display.php?webtag=MOI&msg=3830.4

- Michael