Pathfinder 2e is continuing the original edition's success, but one initially proposed rule could have bogged down the whole game. It's fortunate that the creators ran a playtest period before releasing 2e properly to iron out all the kinks. If not, then the game may have introduced one of the most pointlessly restrictive rules in tabletop gaming.
Before Pathfinder 2e's release, Paizo ran a playtest in order to get player feedback on the changes to the game. This process helped to determine how well the new mechanics introduced in 2e functioned. Making the game feel too different or less fun would be more likely to push away old players than draw in new ones. With Pathfinder likely to see new players starting soon, maintaining the game's quality is important. The playtest was a wise way to make sure that the game was in good shape before publication. One of the most important things to come from 2e's playtest was the trial and removal of a controversial new rule.
Resonance Would Have Restricted Pathfinder Players' Magic Use
In the original plans for Pathfinder 2e, there was a new mechanic called resonance points. Resonance points were a limit on the use of magic items, intended to keep players from overusing them in a campaign. Every character had daily resonance points equal to their level and Charisma modifier combined. Every time a magic item's effect is used, it would use up a resonance point, and once depleted, they had to make a check with each successive use, losing the ability to use magic items for the rest of the day on a fumble. This formed a major difference between Pathfinder and DnD, which has no such rule.
Resonance Was Pathfinder's Most Protested New Mechanic
The problem with resonance started with how few points players got, especially at lower levels. In addition to actively using items, items that granted permanent effects or bonuses, like armor or rings, required investing a point apiece at the beginning of the day. This meant that players would lose resonance points before even doing anything that day. It was likely that players would run out of their limited resonance points quickly, making using magic items far too risky in most cases. Losing the ability to even heal oneself with potions would be devastating if one of Pathfinder's unusual monster encounters took place with a party member's resonance depleted.
The reaction to the resonance mechanic among playtesters was intensely negative. It was seen as an unnecessary restriction that penalized players for using the items that they had collected. Thankfully, Paizo took note of how hated the mechanic was, and it never made it to a printed rulebook. Instead, a new rule placing a limit on the number of magical effects a character could have active simultaneously was implemented. This was seen as an acceptable substitute for the hated resonance mechanic. Thanks to the playtest, resonance points and their many downsides were successfully excised from the game before Pathfinder's second edition books were released.
Resonance points were the biggest misfire out of the proposed rules for Pathfinder 2e, and it's fortunate that they never made it past the playtest period. While it's easy to see what the developers were trying to do with the rule, it was aimed too broadly, creating problems rather than solving them. Had it made it into the game, the resonance system would have been the worst mechanic in Pathfinder.
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