... just figured out the possible cause of the artefacts described in that thread. Texture coordinates should obviously be related to the center of the edge pixels in texture image given in TexSubImage2D. Right now, in the TextureFont class they point to the outside edge of those pixels. Therefore - for linear texture mapping - situations exist, where the neighboring pixels from the texture sheet are used for interpolating the edge pixels in the rasterizing step.
After a short test, it seems the corresponding code in TextureFont should be like this:
rectangle = RectangleF.FromLTRB( (rect.Left + 0.5f) / texture_width, (rect.Top + 0.5f) / texture_height, (rect.Right - 0.5f) / texture_width, (rect.Bottom - 0.5f) / texture_height); loaded_glyphs.Add(g.Character, rectangle);