I grade in batches and I do not necessarily want students to know the order in which I graded their work. I would prefer to have an option for the date/time on SpeedGrader comments to be removed, or to automatically be marked to the time that the assignment was unmuted.
An example of where this has been problematic for students: I did a few papers early from one batch of big research paper drafts. A student saw the early date on my comments and told me how stressed she was because she wished she could have gotten that comment then. I explained to her about the grade release time compared to the time that I actually put the comment in SpeedGrader.
For bigger assignments, I sometimes open up a Google Doc, type the comments in there, and then cut and paste them into SpeedGrader when I've graded everyone's work.