While setting the "created_at" attribute when creating public comments for ideas via the API works smoothly, the same doesn't work for internal comments. The endpoint used is https://quintly.aha.io/api/v1/ideas/<IDEA_ID>/comments as a POST request with the following JSON as an object (I used sample data here as an example). You can quickly validate that instead of using the date provided with "created_at" it does always use the current date/time instead. Expected is it does use the provided "created_at" attribute as the creation time for this private comment.
{"comment":{"body":"<p>test!<\/p>","created_at":"2016-12-03T17:17:09.296Z","user":{"email":"test@test.com"}}}
Due to the low number of votes we are unlikely to make this change in the near future.
Note: You can now set the visibility of portal comments. Instead of creating internal comments on the idea, you might prefer to add portal comments with visibility set to employees only.
Just strange, that you can set it for public comments, but not for private comments... At least setting the user works and updating the description works...