But that's the problem. Upvoting and approving/moderating are different things. Upvoting is a subjective exercise, whereby you signal substantive agreement. Approving/moderating is an objective exercise, whereby you signal that a comment meets minimal community standards of tone and non-triviality. Conflating those will inhibit dissenting opinion.

That said, the direction you're implying might be an improvement. Rather than a separate Pending Comments list, mod-level users would be able to see pending comments in the context of the parent item/tree, but with some kind of adornment or different color. Pending comments will also have a 'tolerable'/'civil'/'endorse' link next to it, but no up/down vote buttons. Only after it's been deemed tolerable enough, will a pending comment become live/approved and have up/down buttons.