If I had to guess, I would say there are more ProofBuddy users hosting on GoDaddy that any other host. I've never actually counted, but it sure seems like a popular place to host. So it amazes me that it's taken so long for me to learn that GoDaddy has two different versions of ImageMagick on their servers.
So why does it matter if they have two different versions? Because the version that is used by default is version 5 and about 6 years out of date. The biggest loss is no sepia toning in the old version, but as I found out this morning the old version also doesn't work well with watermarking. Instead of overlaying a transparent PNG like it should, version 5 just puts a semi-transparent white box where the watermark should go. Obviously not the correct look.
Up until today I've always recommended GoDaddy users change the setting on Options -> Images to use the GD library instead of ImageMagick. But with version 6 also on their servers you really should be using ImageMagick.
Fortunately it's an easy change to make. On the Options -> Images tab you'll need to make sure that the dropdown next to Image Conversions is set to ImageMagick. Then set the ImageMagick path field to /usr/local/bin . It may have been /usr/bin which is the path to ImageMagick 5 or it may have been blank. Either way it was using version 5.
Here's a screenshot for the visual learners among us.