In a similar vein, will they show up in my view of posts-to-review? (Reviewable posts? Unsure of term.)
If I can't currently see them, can I? It might be a way to allow people to rescue a borderline post.
No, you currently cannot.
If this were implemented, all user information about the flag would have to be stripped from the flag.
It runs somewhat antithetical to the transparency that exists on SO in general (with the exception of voting), so I'm not sure how much of a good idea this is.
I can imagine the influx of questions on meta: "why do I have so many flags on my posts". Combine that with the current disaster that is flag weight and I'd have to say that I don't see how a feature like this could be helpful.
As for the statement:
While it might be a way to rescue a borderline post, as there are a number of ways that a borderline post can be saved without a flag:
Flagging these posts in instances where you can do the work is simply adding noise to the system. Furthermore, flagging these for moderator attention (this is not directed at you, but a general statement) is even more egregious, in that it takes a moderator's time away from content that deserves moderator attention.
If a post is flagged, it generally means that there is something wrong with it that can be dealt with in no other way except to flag it.
If it's a borderline post that can be rescued then take the action required to rescue it, do not flag it.