I was wondering for a long time what was going on, no I can finally reproduce it.
It's a minor thing with an easy workaround, but anyway:
Using the "draw text" block in an actor behavior will normally draw the text relative to the top left of the actor. But if you anchor an actor to screen and draw text at (0,0) in a behavior for this actor, it will not draw at the top left of the actor, but at the center of the actor.
Edit: Oh, wait, it turns out to be even more obscure: it only happens when the actor has disabled physics.
Workaround: Putting a "switch to actor space for Self" in the beginning of "when drawing" fixes this, but I think this should not be necessary.