Quill Fixup. Make sure to adjust the name filter in FixupPostprocessor for your pipeline BEFORE you drop these into an Editor folder.

Fixup.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System.Linq;

namespace pfc.WeirdQuillFixup
{
    public static class Fixup
    {
        public static void FixMeshInPlace(Mesh mesh)
        {
            var vs = mesh.vertices;
            var cs = mesh.colors;
            var ind = mesh.GetTriangles(0);

            var avg = Vector3.zero;
            var min = Mathf.Infinity;
            var max = Mathf.NegativeInfinity;

            var threshold = 1f;
            var toDiscard = 0;

            min = Mathf.Infinity;
            max = Mathf.NegativeInfinity;

            List<int> trianglesToDiscard = new List<int>();

            // find broken triangles
            for (int i = 0; i < ind.Length; i += 3)
            {
                if (
                    CheckEdge(vs[ind[i + 0]], vs[ind[i + 1]], ref min, ref max, threshold) ||
                    CheckEdge(vs[ind[i + 1]], vs[ind[i + 2]], ref min, ref max, threshold) ||
                    CheckEdge(vs[ind[i + 2]], vs[ind[i + 0]], ref min, ref max, threshold))
                {
                    trianglesToDiscard.Add(i + 0);
                    trianglesToDiscard.Add(i + 1);
                    trianglesToDiscard.Add(i + 2);
                }
            }

            avg /= vs.Length;

            toDiscard += trianglesToDiscard.Count;
            var copy = ind.ToList();
            for (int j = trianglesToDiscard.Count - 1; j >= 0; j--)
            {
                copy.RemoveAt(trianglesToDiscard[j]);
            }

            mesh.SetTriangles(copy, 0);
            mesh.Optimize();
            mesh.RecalculateBounds();
        }

        public static bool CheckEdge(Vector3 a, Vector3 b, ref float min, ref float max, float threshold)
        {
            if (a.sqrMagnitude == 0 || b.sqrMagnitude == 0) return true;
            return false;
        }
    }
}

FixupPostprocessor.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;

namespace pfc.WeirdQuillFixup
{
    // Adds a mesh collider to each game object that contains collider in its name
    public class Example : AssetPostprocessor
    {
        void OnPostprocessModel(GameObject g)
        {
            // Make sure you have a clear naming scheme for your Quill files and detect it here.
            // Otherwise, other meshes in your project will get "fixed" and most likely become corrupt!
            if (!g.name.Contains("Quill")) return;

            Debug.Log("Postprocessing " + g.name);

            var mfs = g.GetComponentsInChildren<MeshFilter>();
            foreach (var mf in mfs)
                Fixup.FixMeshInPlace(mf.sharedMesh);
        }
    }
}