The entered comment of Event Rule Overrides is expected to be saved into the Comment_vod__c field on the EM_Event_History_vod__c object:
Why is the entered comment of Event Rule Overrides saved in Event History with two colons?
This is working as designed.
The override feature captures and records two different pieces of information into the Comment field:
- The text that is displayed in the warning
- The comment entered by the user into the comment box
The two pieces of information are concatenated into a single string, separated by two colons.
CRM Help Documentation: Event Rule Overrides