On the single piece of "autoflag transparency", a thought, or several
(by the way, this was the first I heard of the project. As a somewhat empowered by rep user (I know better than to put myself up for moderator - I have cranky days) on several sites, I have been known in the past to deal with "the truly vile" by spam-flagging and then editing to take it off-screen unless you looked at the edit history. Most of the rest seemed to go away fast enough on the sites I frequent.)
Rather than needing accounts with special privileges such as "multiple flags per post" make, and register system-wide, 5 accounts. CharcoalAutoflag1 through 5, say, or come up with something better. They would perhaps need extra flagging volume, but nothing special flag-per-post. They simply pile on in the same way that real people do. Indeed, if they are accurate, they could even get their extra flagging volume the same way real users do, by having their flags classified as helpful.
If it's:
99% spam, CharcoalAutoflag1 flags it.
99.5 CharcoalAutoflag2 also flags it
99.75 CharcoalAutoflag3 also flags it
99.95 CharcoalAutoflag4 also flags it
99.99 CharcoalAutoflag5 also flags it (or 99.999 or however many decimal places you want to put there.)
I agree with the general idea that the automated flagging seems good from a spam-removal view, but if it's pretending to be real users doing the flagging, it's not at all apparent if a post is being flagged by people or bots. Having whichever account correlates to the highest level of certainty post a comment to the effect that "Charcoal's automated spam detection evaluates this post as 99.5% likely to be spam" or similar message would also be helpful (perhaps you are doing this, I've hardly spent the evening combing though the whole backstory to formulate the commentary on a small part of the process I had not known about until today.)