My apologies if this has been discussed before but I was hoping to clear things up, or at least see how you play it.

On page 33 it says "A Demeanour may be triggered a maximum of once (and only once, no matter how many Demeanours he may have!)".

Correct me if I'm wrong but doesn't every PC have two demeanours. No more, no less? Or would it be referring to page 32 which says that your Personal Demeanour can change over time, thus implying that it could be interpreted to mean you have multiple?

With the latter in mind, can you only trigger a single demeanour per session or does it mean you can trigger your Chapter one once and your Personal one once? The confusion (for me, but probably not for anyone else ) lies in the next sentence:

"Triggering a Space Marine's Demeanours...."

Demeanour S , plural.

I know for a fact one of my players will pick up on this and claim it means once PER Demeanour which I consider too powerful considering the amount of Fate Points a DW PC begins with.

How do you interpret the text? Please help my tiny brain to understand!!

I believe technically, its only once per session, chapter or personal.

But really, I don't see why a GM wouldn't just allow both, primarilly if the rp behind each use is solid.

Correct, you can trigger once per session, using either of your demeanours.