In Standard Brawl, playing Azula vs The Serpent Society. When the opponent casts his Commander (The Serpent Society), I attempt to counter it with Mana Sculpt, while controlling a Wizard (Harmonized Trio).

Despite the fact that Ward should not be active on the stack (The Serpent Society is a spell on the Stack, thus should not have its Creature abilities), Ward is triggered, and I'm prompted with "Are you sure you want to play this, if you cannot pay the Ward cost, the spell will be countered". I confirm, since I could pay the Ward cost (Take 5 Poison counters).

Arena does not give me the opportunity to take ward counters, instead Serpent Society resolves, but I also get 3 Mana from Mana Sculpt the next main phase.

As far as I can tell they had nothing that would have given The Serpent Society "Can't be countered" which would be consistent with the behavior.

Later in the game Ward triggered and resolved as expected when playing a removal spell.