After Bug 19791 was implemented, it was discovered that the comment field has substitution methods. Because of this, any % in the input text has to be escaped to %%
See also ImageMagick documentation on properties
http://www.imagemagick.org/script/escape.php?ImageMagick=i766ho1om315scce8eh75efjc6
Version: 1.16.x
Severity: major