Why Flocke Can't Change His Appearance (other than to Smokey) by The Scribe

Two people knew about Flocke's "predicament" of not being able to change his appearance: Illana and himself.

I kept wondering about what might've happened to trap him in the body - was it something to do with Locke's real body being buried, etc, like others were speculating... I couldn't see it being anything so simple - after all, if it were, Flocke could just have had Sayid or Claire dig the body up.

No.. something had to be destroyed. Something important.

JACOB'S CABIN.

I was quite surprised in Season 5 when Illana mentioned that somebody else had been "using it" - and that she then set it alight.

Can you imagine how difficult it would've been for them to know who MIB was if he was still able to change appearance? He could've popped up as anyone and caused chaos... especially since he was free and able to kill who he liked - thereby giving him the ability to take over their appearance.

When Illana burnt down the cabin, she was removing him of this ability. Illana must've seen the cabin before - and seen Jacob use it to change his own appearance for some reason.

With this in mind, is it possible that the ash around the cabin also wasn't to keep anyone in - it was to keep MIB/Smokey out.