Although it's clearly not -1 for every metamagic feat used (not sure where that was pulled out of, though I have a pretty good idea) stacking is not ruled out.
"Treat its actual level as 1 lower for determining the spell's final adjusted level" implies that other adjustments can be made before changes to the final adjusted level happen. Next, see the text for Wayang Spellhunter:Wayang Spellhunter wrote:When you use the chosen spell with a metamagic feat, it uses up a spell slot one level lower than it normally would.
The text reads "a spell slot lower;" not "a spell slot lower per feat used." It also does not modify the final adjusted level.
Wayang Spellhunter grants -1 to the spell level, then Magical Lineage makes the final adjusted level 1 level lower. In this case it's 7-2 to a final level of 5.
Hi Katydid, completely concur. That's my understanding too.
On an added note, here's a curveball for you all: the DM in the Campaign in question, has allowed another player to use the old 3.5 feat; Arcane Thesis which essentially allowed you to cast spells as though they were were at Caster Level +2 AND apply a -1 spell level reduction PER Metamagic Feat applied.
IMHO the original ruling of this feat is broken else you could apply 4 Metamagic feats to a Scorching Ray and cast it as something insane like a Level 5 spell.
Although I heard there was a revised errata for the Player's Handbook II (between 2007 and 2009) which effectively nerfed Arcane Thesis down to "-1 *total* spell level reduction, regardless of the number of Metamagic feats applied" bringing it more in line with the effects of Magical Lineage.
Any thoughts on how that would work with either a Max'ed and Emp'ed Scorching Ray or Fireball (at say, a given Caster Level) ?