In some offerings, we want to make it mandatory for the end user to add a comment before accepting a solution, not only when rejecting.
It is for audit. Some times we need more confirmation than pressing Accept.
One scenario is where the service request offering gives a new user access to a system. The offering has automated tasks giving access via OO, but the requester has to perform some manual steps afterwards. For audit reasons we need the user to confirm his manual task in words, not only press Accept. There are several scenarios where a mandatory comment is very usefull.