It might be done on purpose, as a penalty, but even if it is that doesn't mean it's a good way of doing things.
If you try to play a critter with the board already full, you get a message and nothing else happens.
That's what should happen when you try to hasten with a full hand, or use queen or deja vu with the board full, or play animate weapon with no weapon.
Likewise, cancelled abilities should be properly cancelled, i.e. not have cost you the use of that ability nor the quanta.
As for the suggestion, I'd like a discard button too. Once that's in place, make attepmts to end turn with eight cards simply show a message and nothing more.