Dragonlance Campaign Setting has a feat called Reserves of Strength. This is the complete text of its benefit:
When you cast a spell, you can decide to increase your caster level with that spell by 1, 2, or 3, but you are stunned for an equal number of rounds immediately after doing so. Your increased caster level affects all level-based variables of the spell, including range, area of effect, spell penetration, and the difficulty of dispelling the spell. You can exceed the normal level-fixed limits of a spell with this feat, so a 9th-level wizard could use Reserves of Strength to cast a Fireball as a 12th-level wizard and deal 12d6 fire damage.
If you are not subject to stunning effects, you instead suffer 1d6, 3d6, or 5d6 points of damage when you call upon your Reserves of Strength feat.
(Dragonlance Campaign Setting pg. 86, emphasis mine)
The bolded portion is the one that gets the most attention: it allows spells to exceed their usual caster level cap, potentially allowing vastly more powerful effects from the same spell slot. In practice, it tends not to matter very much at all—usually spells become obsolete well before hitting their caps anyway—but certain spells, particularly when combined with other shenanigans to boost caster level absurdly high, are quite broken by this feat.
Some claim, however, that the feat cannot do this: that the feat is limited only to exceeding that limit by the 1, 2, or 3 you add to your caster level with the rest of the feat, and not any other source of caster level—be it simply being high level, or having tons of bonuses—can exceed that limitation.
Is there anything in the text of the feat itself that supports that claim?
Note that, in a sense, there are two aspects to this claim: that you can only benefit from the limit-exceeding benefit while using the CL-for-stun trade, and secondarily, that the limit-exceeding benefit applies only to the CL from the CL-for-stun trade, and not to CL from any other source. It would be sufficient to address only the second (since if the limit-exceedingly only applies to the bonus from the trade, you obviously have to be making the trade), but it would be insufficient to address only whether the trade needs to be taking place. The primary concern is whether or not the feat allows arbitrarily-high CLs to be used; whether or not you must takes a stun or d6 of damage in order to gain that benefit is a secondary concern.
This question is not about balance, nor is it about what anyone thinks the feat should say, or even about what we suspect the authors may or may not have meant the feat to do: this is purely about what the text in the feat itself, as published, says, and if there is any way to justify that limitation within the feat’s own text.