One interesting excerpt from chapter 22 shows the scaffold as part of the nature of Hester Prynne. It is because Hester's rebellious nature keeps her enslaved to certain things, behaviors, and emotions. For this reason, sometimes the scaffold represents a part of her that she cannot totally shake off, or move on from.
In chapter 22, "The Procession", Dimmesdale is more enrapturing than ever in the Election Day sermon. As such, Hester becomes enraptured by his melodic voice. She manages to be near the scaffold, the same place where her notoriety was born. Why should Hester continue to gravitate there, especially when Dimmesdale's voice is hypnotizing her to a point? It is because the entire relationship is represented with the symbol of the scaffold: its punishment, and its notoriety. Hester cannot move on from Dimmesdale. She cannot move on from her personal scaffold.
An irresistible feeling kept Hester near the spot [...] she took up her position close beside the scaffold of the pillory. It was in sufficient proximity to bring the whole sermon to her ears, in the shape of an indistinct but varied murmur and flow of the minister's very peculiar voice.
The voice of the minister "breathed passion, and pathos, and emotions" that spoke straight "to the human heart". Hester was there, completely taken by the words of Dimmesdale, whom she still loves. Again, her stay at the scaffold mirrors completely the way that she has not been able to move away from her feelings for Dimmesdale even years after their relationship had been consummated. She still suffers because of him. She still suffers at the scaffold that has become her life. Somewhere inside of her feels that this is a part of her reality, and she accepts it as such. Therefore, stuck at the scaffold of her existence as she may be, she still manages to relish with passion the voice and words of the man with whom she fell in love so deeply.
During all this time, Hester stood, statue-like, at the foot of the scaffold. If the minister's voice had not kept her there, there would, nevertheless, have been an inevitable magnetism in that spot, whence she dated the first hour of her life of ignominy.
Most importantly, becoming "the woman of the scarlet letter" gave her a sense of self that she had never felt before. As a woman of her time, Hester may have never had learned what it is to struggle, fight for one's dignity, or defend those whom she loves. She would have merely gone through life as one of many other unhappy wives who try to live day after day in a boring existence. Instead, the scarlet letter, which she accepted in the scaffold, brought upon her a new sense of self. This is another thing that she cannot escape. The scaffold was her stage. It is the place that brought her chaos into some form of order.
There was a sense within her--too ill-defined to be made a thought, but weighing heavily on her mind--that her whole orb of life, both before and after, was connected with this spot, as with the one point that gave it unity.
Therefore, the scaffold is everything: Hester's life, her identity, her punishment, her nature, her pain, her pleasure and everything that she has now become.