When using Xflow Tasks, it is possible to configure the presented fields as Read Only or Required at Xflow Interface/View Configuration/Detail View, but I can't find a place where to configure the Description field as Read Only.
As this field comes from the WF Template, normally has instructions on how to proceed, and should not be changed.
Release : 17.3 RU19 or lower
CA Service Desk Manager
The fix to address the issue will be included in the forthcoming RU21 patch release