Hi, i'm just answering this so the answer gets archived in the internets.
You can set a font texture properties manually using code, so if you have textmesh and want to set it to point filtering,
do a script with:
TextMesh text = GetComponent<TextMesh>();
text.font.material.mainTexture.filterMode = FilterMode.Point;
And it should work just fine.
Be aware that this modifies the asset itself, so all the renderers using this texture will get the change too.