This is not strictly true. The stacking rules apply to bonuses. It says so right in the header - "Bonuses" if you're looking in the RC, or "Bonus Types" if you're looking in the DMG (in an amusing coincidence, both sections happen to fall on page 21 in their respective books). If something isn't a bonus, then the stacking rules never come in to play. So what's a bonus? Conveniently, the PHB gives us a definition: A positive modifier to a die roll. Level Adjustment is not a positive modifier to a die roll, so it's not a bonus, and so the stacking rules do not apply.
Going to stop you right there before you go full retard on me Link.
The question is can or can't you stack a
same source value by taking the same Template multiple times (minor tangent, something LM says you can't do to begin with). The two major fronts on this is if it were a bonus, then to logically follow that through it'd be unnamed and thus stacks. I refuted the possibility that it'd be a bonus, implied for all we know it'd be an
effect which doesn't stack. Your reply was to prove that it's not a bonus and then immediately attempt a propositional fallacy, if it's not a
bonus then it's not an
effect either. Which of course drew my response of what the fuck man? But about one third of the way into pointing out that propositional logic being one of the reasons why we should all support eugenics I actually found my self thinking what if Link is still just prattling off about stuff he doesn't know? Like I'd love to see him explain how I can't stack wearing Leather & Full-Plate together because your AC isn't a rolled value so "armor bonus" can't be a
bonus Anyway, I figured when I said effect you simply have no idea what I meant. The
Stacking Effects govern most everything in the game, and it's what I meant by
effects.
All items be it magical or alchemical or not as well as breath effects, draconic auras, soulmelds, invocations, martial powers, mysteries, psionic powers, utterances, and even vestiges all directly follow those rules even through many of their respective sources didn't initially say such and many of those are not even magical (like many maneuvers are extraordinary abilities).
If Templates were also meant to be treated as such, which the Evolved Entry in Libris Mortis supports, that would mean attempting to take the same Template again wouldn't change your LA. But more to the point, it also wouldn't provide you with another set of bonuses to your Ability Scores or new Special Abilities since none of those stack to begin with. To copy the Feat entry, "in general, having a template twice is the same as having it once."
It that interpretation directly supported by RAW? No.
But it's better than falsely summarizing bonuses then claiming Templates are not one as support to concluding that Templates are not effects and pushing that pile of self-disrespecting shit on people like it's fact.