Fact
Per Wowhead (Oct 9), a recent beta build penalizes downranking: the character sheet's Spell Damage and Spell Healing tooltips say spells cast using ranks 'vastly below your current level' get less benefit from Spell Damage and Spell Healing and have a reduced chance to activate class abilities and talents (Frostbite and Omen of Clarity are the examples given). A developer note says a Rank 1 Frostbolt at level 60 has a 0% chance to activate Frostbite. No formula or level cutoff is published. This matters most to healers who downrank to save Mana.