Symptoms

The comments supplied by workflow approvers via a SharePoint Workflow Integration (SPWI) process are no longer being displayed.
These comments are still being captured, and saved, but are not visible on the task pages for subsequent SPWI tasks within the same workflow.
 

Diagnoses

Comments from SharePoint Workflow Integration (SPWI) processes are stored in an XML field titled SPComments.
There are two primary ways these comments can be surfaced at design time.
1. In the Context Browser as a hidden XML field under Process/Activity Data
2. Using a custom inline function to access and consume the XML (for more info, see: http://community.k2.com/t5/K2-blackpearl/Get-SPComments-Custom-Inline-function/ba-p/1023)

It was found that the custom inline function had been installed in the Test environment, but removed from the Production environment.
 

Resolution

To get the "SPComments" to show up in Production, download the custom inline function from the Community Market, and install it, per the included instructions.