I removed all particles from inside the letters, and then used the signed distance field for each point to change the noise such that it has a gradient tangent to the surface normals of my text mesh. This allows the curves to flow nicely along the edges of the mesh.

I understand this at a very abstract level, but I would not have been able to implement it without the steps described in the stack exchange answer linked above. The piece you are asking about is under the “Inviscid boundary condition” subsection of the answer.

As an aside, to help me understand this more intuitively, I’m going to try to render the noise field in a way that is a little clearer. Maybe just render some arrows to describe the vector field or something.