Instagram client for Windows Phone 6tag has found another update today, bringing the version number to 4.1.1.
With it comes a fix for those utilizing the optional black/white margins using the auto fit mode (aka full image posting). This tool is useful for publishing full, non-square photos to Instagram while retaining the whole view. This is accomplished through the use of top and bottom margins like a letterbox in film.
Starting with the previous 4.1 update, when cropping or using a square shot, the new improved image quality algorithm was being applied. However, some users were complaining about the IQ degrading when using the white or black margins, resulting in "blurry" pictures. Evidently, the new improved IQ was not being applied to this method of image non-cropping.
Now, with today's update that should be much improved, so give it a shot!
Thanks, Sahil R., Prasoon C., and Medgeek, for the tips!