When scaling text using DrawString the text doesn't stretch, simply moves apart, and the source drawing rectangle seems to pull in image data from adjacent characters.
 
spriteBatch.DrawString(this.font, this.text, this.position, this.color, 0.0f, size, scale, SpriteEffects.None, 0);
 
In the example, scaling was set to 1.2. Image of result attached.