Clandestino,
Sorry, the information that the Q400 isn't prone to tailplane stall didn't "leak out only after the accident"
I quote from the AOM, Chapter 3 abnormal and emergency procedures. Page 3.4.23, section 3.4.6.5 This is from revision 7 dated 16 march 2001 should you wish to refer to it.
Landing
If landing flap selection is accompanied by stick force lightning or stick force irregularities, immediately retract flap to previous setting and cycle the de-ice boots several times. If practicable, land using a lower landing flap setting. This condition, which is the precursor to tailplane stall, will not occur unless the AOM icing procedure are not followed.
The bold emphasis is mine but it isn't anything new. I have had that manual since 2001, almost eight years before this accident occured.