Can't accept level up or quest rewards if your inventory is full. Doesn't matter if you don't give a crap about the crown fortifying meal, or the green Jerkin of Ddahlmoronhonima's Blessing. If you don't have the space for all of it, you're not getting any of it. That sucks ass.

I think that every time you level up or complete a quest but don't have enough inventory space for the rewards, what you don't have space for should be sent to your in-game mail instead. That way, you can't be prevented from levelling up or completing a quest because your inventory is full of ***.