When creating an imagefont, the spacer color is not removed from the image. There is code to do this, but it is applied to the wrong data. The following test case will demonstrate the issue. Initialize the data with this code.
id = love.image.newImageData("imagefont.png") image = love.graphics.newImage(id) font = love.graphics.newImageFont(image, "1234") image2 = love.graphics.newImage(id)
When I displayed image and image2 in the draw callback, I saw that image2 had had the spacer color removed and replaced by transparency, but image had not. This implies the code to replace the color is applied to the imagedata, but does not affect the image.
The spacer color is also not removed when loading an imagefont directly from file. To see this, simply create a suitable imagefont file and include the spacer color in the middle of a font glyph subimage. It should not become transparent, as it did not do so for me.